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yanglbmeyanglbme
authoredSep 15, 2023
feat: add solutions to lcci problem: No.16.26 (#1629)
No.16.26.Calculator
·
v0.3.0v0.2.0
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‎lcci/16.26.Calculator/README.md

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## 题目描述
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<!-- 这里写题目描述 -->
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<p>给定一个包含正整数、加(+)、减(-)、乘(*)、除(/)的算数表达式(括号除外)，计算其结果。</p>
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<p>表达式仅包含非负整数，<code>+</code>， <code>-</code> ，<code>*</code>，<code>/</code> 四种运算符和空格&nbsp;<code>&nbsp;</code>。 整数除法仅保留整数部分。</p>
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<p><strong>示例&nbsp;1:</strong></p>
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## 解法
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<!-- 这里可写通用的实现逻辑 -->
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**方法一：栈**
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我们可以用一个栈来保存数字，每次遇到运算符时，就将数字压入栈中。对于加减法，由于其优先级最低，我们可以直接将数字压入栈中；对于乘除法，由于其优先级较高，我们需要将栈顶元素取出，与当前数字进行乘除运算，再将结果压入栈中。
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最后，将栈中所有元素求和即为答案。
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时间复杂度 $O(n)$，空间复杂度 $O(n)$。其中 $n$ 为字符串长度。
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<!-- tabs:start -->
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### **Python3**
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<!-- 这里可写当前语言的特殊实现逻辑 -->
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```python
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class Solution:
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def calculate(self, s: str) -> int:
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n = len(s)
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x = 0
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sign = "+"
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stk = []
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for i, c in enumerate(s):
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if c.isdigit():
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x = x * 10 + ord(c) - ord("0")
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if i == n - 1 or c in "+-*/":
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match sign:
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case "+":
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stk.append(x)
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case "-":
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stk.append(-x)
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case "*":
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stk.append(stk.pop() * x)
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case "/":
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stk.append(int(stk.pop() / x))
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x = 0
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sign = c
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return sum(stk)
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```
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### **Java**
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<!-- 这里可写当前语言的特殊实现逻辑 -->
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```java
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class Solution {
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public int calculate(String s) {
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int n = s.length();
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int x = 0;
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char sign = '+';
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Deque<Integer> stk = new ArrayDeque<>();
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for (int i = 0; i < n; ++i) {
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char c = s.charAt(i);
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if (Character.isDigit(c)) {
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x = x * 10 + (c - '0');
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}
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if (i == n - 1 || !Character.isDigit(c) && c != ' ') {
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switch (sign) {
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case '+' -> stk.push(x);
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case '-' -> stk.push(-x);
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case '*' -> stk.push(stk.pop() * x);
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case '/' -> stk.push(stk.pop() / x);
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}
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x = 0;
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sign = c;
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}
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}
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int ans = 0;
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while (!stk.isEmpty()) {
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ans += stk.pop();
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}
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return ans;
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}
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}
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```
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### **C++**
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```cpp
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class Solution {
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public:
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int calculate(string s) {
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int n = s.size();
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int x = 0;
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char sign = '+';
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stack<int> stk;
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for (int i = 0; i < n; ++i) {
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char c = s[i];
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if (isdigit(c)) {
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x = x * 10 + (c - '0');
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}
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if (i == n - 1 || !isdigit(c) && c != ' ') {
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if (sign == '+') {
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stk.push(x);
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} else if (sign == '-') {
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stk.push(-x);
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} else if (sign == '*') {
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int y = stk.top();
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stk.pop();
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stk.push(y * x);
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} else if (sign == '/') {
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int y = stk.top();
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stk.pop();
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stk.push(y / x);
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}
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x = 0;
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sign = c;
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}
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}
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int ans = 0;
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while (!stk.empty()) {
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ans += stk.top();
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stk.pop();
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}
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return ans;
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}
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};
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```
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### **Go**
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```go
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func calculate(s string) (ans int) {
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n := len(s)
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x := 0
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sign := '+'
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stk := []int{}
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for i := range s {
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if s[i] >= '0' && s[i] <= '9' {
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x = x*10 + int(s[i]-'0')
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}
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if i == n-1 || (s[i] != ' ' && (s[i] < '0' || s[i] > '9')) {
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switch sign {
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case '+':
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stk = append(stk, x)
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case '-':
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stk = append(stk, -x)
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case '*':
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stk[len(stk)-1] *= x
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case '/':
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stk[len(stk)-1] /= x
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}
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x = 0
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sign = rune(s[i])
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}
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}
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for _, x := range stk {
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ans += x
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}
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return
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}
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```
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### **TypeScript**
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```ts
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function calculate(s: string): number {
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const n = s.length;
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let x = 0;
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let sign = '+';
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const stk: number[] = [];
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for (let i = 0; i < n; ++i) {
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if (!isNaN(Number(s[i])) && s[i] !== ' ') {
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x = x * 10 + s[i].charCodeAt(0) - '0'.charCodeAt(0);
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}
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if (i === n - 1 || (isNaN(Number(s[i])) && s[i] !== ' ')) {
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switch (sign) {
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case '+':
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stk.push(x);
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break;
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case '-':
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stk.push(-x);
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break;
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case '*':
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stk.push(stk.pop()! * x);
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break;
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default:
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stk.push((stk.pop()! / x) | 0);
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}
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x = 0;
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sign = s[i];
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}
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}
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return stk.reduce((x, y) => x + y);
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}
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```
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### **...**

‎lcci/16.26.Calculator/README_EN.md

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### **Python3**
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```python
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class Solution:
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def calculate(self, s: str) -> int:
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n = len(s)
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x = 0
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sign = "+"
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stk = []
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for i, c in enumerate(s):
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if c.isdigit():
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x = x * 10 + ord(c) - ord("0")
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if i == n - 1 or c in "+-*/":
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match sign:
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case "+":
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stk.append(x)
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case "-":
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stk.append(-x)
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case "*":
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stk.append(stk.pop() * x)
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case "/":
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stk.append(int(stk.pop() / x))
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x = 0
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sign = c
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return sum(stk)
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```
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### **Java**
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```java
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class Solution {
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public int calculate(String s) {
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int n = s.length();
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int x = 0;
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char sign = '+';
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Deque<Integer> stk = new ArrayDeque<>();
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for (int i = 0; i < n; ++i) {
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char c = s.charAt(i);
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if (Character.isDigit(c)) {
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x = x * 10 + (c - '0');
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}
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if (i == n - 1 || !Character.isDigit(c) && c != ' ') {
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switch (sign) {
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case '+' -> stk.push(x);
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case '-' -> stk.push(-x);
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case '*' -> stk.push(stk.pop() * x);
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case '/' -> stk.push(stk.pop() / x);
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}
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x = 0;
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sign = c;
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}
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}
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int ans = 0;
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while (!stk.isEmpty()) {
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ans += stk.pop();
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}
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return ans;
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}
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}
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```
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### **C++**
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```cpp
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class Solution {
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public:
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int calculate(string s) {
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int n = s.size();
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int x = 0;
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char sign = '+';
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stack<int> stk;
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for (int i = 0; i < n; ++i) {
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char c = s[i];
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if (isdigit(c)) {
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x = x * 10 + (c - '0');
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}
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if (i == n - 1 || !isdigit(c) && c != ' ') {
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if (sign == '+') {
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stk.push(x);
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} else if (sign == '-') {
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stk.push(-x);
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} else if (sign == '*') {
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int y = stk.top();
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stk.pop();
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stk.push(y * x);
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} else if (sign == '/') {
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int y = stk.top();
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stk.pop();
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stk.push(y / x);
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}
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x = 0;
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sign = c;
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}
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}
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int ans = 0;
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while (!stk.empty()) {
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ans += stk.top();
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stk.pop();
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}
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return ans;
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}
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};
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```
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### **Go**
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```go
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func calculate(s string) (ans int) {
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n := len(s)
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x := 0
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sign := '+'
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stk := []int{}
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for i := range s {
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if s[i] >= '0' && s[i] <= '9' {
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x = x*10 + int(s[i]-'0')
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}
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if i == n-1 || (s[i] != ' ' && (s[i] < '0' || s[i] > '9')) {
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switch sign {
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case '+':
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stk = append(stk, x)
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case '-':
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stk = append(stk, -x)
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case '*':
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stk[len(stk)-1] *= x
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case '/':
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stk[len(stk)-1] /= x
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}
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x = 0
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sign = rune(s[i])
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}
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}
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for _, x := range stk {
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ans += x
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}
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return
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}
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```
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### **TypeScript**
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```ts
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function calculate(s: string): number {
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const n = s.length;
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let x = 0;
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let sign = '+';
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const stk: number[] = [];
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for (let i = 0; i < n; ++i) {
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if (!isNaN(Number(s[i])) && s[i] !== ' ') {
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x = x * 10 + s[i].charCodeAt(0) - '0'.charCodeAt(0);
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}
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if (i === n - 1 || (isNaN(Number(s[i])) && s[i] !== ' ')) {
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switch (sign) {
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case '+':
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stk.push(x);
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break;
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case '-':
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stk.push(-x);
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break;
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case '*':
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stk.push(stk.pop()! * x);
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break;
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default:
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stk.push((stk.pop()! / x) | 0);
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}
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x = 0;
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sign = s[i];
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}
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}
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return stk.reduce((x, y) => x + y);
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}
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```
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### **...**

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