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feat: add solutions to lc problem: No.2000
No.2000.Reverse Prefix of Word
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-30
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8 files changed

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-30
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‎solution/2000-2099/2000.Reverse Prefix of Word/README.md

+36-10
Original file line numberDiff line numberDiff line change
@@ -54,6 +54,12 @@
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<!-- 这里可写通用的实现逻辑 -->
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**方法一：模拟**
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我们先找到字符 $ch$ 第一次出现的下标 $i$，然后反转从下标 $0$ 开始、直到下标 $i$ 结束（含下标 $i$）的那段字符，最后将反转后的字符串与下标 $i + 1$ 开始的字符串拼接即可。
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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 $word$ 的长度。
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<!-- tabs:start -->
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### **Python3**
@@ -73,14 +79,30 @@ class Solution:
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```java
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class Solution {
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public String reversePrefix(String word, char ch) {
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int j = word.indexOf(ch);
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if (j == -1) {
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return word;
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}
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char[] cs = word.toCharArray();
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for (int i = 0; i < j; ++i, --j) {
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char t = cs[i];
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cs[i] = cs[j];
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cs[j] = t;
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}
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return String.valueOf(cs);
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}
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}
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```
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```java
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class Solution {
77100
public String reversePrefix(String word, char ch) {
78-
int i = word.indexOf(ch);
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return i == -1 ? word
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: new StringBuilder(word.substring(0, i + 1))
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.reverse()
82-
.append(word.substring(i + 1))
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.toString();
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int j = word.indexOf(ch);
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if (j == -1) {
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return word;
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}
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return new StringBuilder(word.substring(0, j + 1)).reverse().append(word.substring(j + 1)).toString();
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}
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}
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```
@@ -92,7 +114,9 @@ class Solution {
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public:
93115
string reversePrefix(string word, char ch) {
94116
int i = word.find(ch);
95-
if (i != string::npos) reverse(word.begin(), word.begin() + i + 1);
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if (i != string::npos) {
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reverse(word.begin(), word.begin() + i + 1);
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}
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return word;
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}
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};
@@ -119,9 +143,11 @@ func reversePrefix(word string, ch byte) string {
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120144
```ts
121145
function reversePrefix(word: string, ch: string): string {
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let idx = word.indexOf(ch) + 1;
123-
if (!idx) return word;
124-
return [...word.substring(0, idx)].reverse().join('') + word.substring(idx);
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const i = word.indexOf(ch) + 1;
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if (!i) {
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return word;
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}
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return [...word.slice(0, i)].reverse().join('') + word.slice(i);
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}
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```
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‎solution/2000-2099/2000.Reverse Prefix of Word/README_EN.md

+30-10
Original file line numberDiff line numberDiff line change
@@ -66,14 +66,30 @@ class Solution:
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```java
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class Solution {
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public String reversePrefix(String word, char ch) {
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int j = word.indexOf(ch);
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if (j == -1) {
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return word;
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}
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char[] cs = word.toCharArray();
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for (int i = 0; i < j; ++i, --j) {
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char t = cs[i];
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cs[i] = cs[j];
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cs[j] = t;
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}
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return String.valueOf(cs);
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}
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}
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```
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```java
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class Solution {
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public String reversePrefix(String word, char ch) {
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int i = word.indexOf(ch);
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return i == -1 ? word
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: new StringBuilder(word.substring(0, i + 1))
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.reverse()
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.append(word.substring(i + 1))
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.toString();
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int j = word.indexOf(ch);
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if (j == -1) {
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return word;
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}
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return new StringBuilder(word.substring(0, j + 1)).reverse().append(word.substring(j + 1)).toString();
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}
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}
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```
@@ -85,7 +101,9 @@ class Solution {
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public:
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string reversePrefix(string word, char ch) {
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int i = word.find(ch);
88-
if (i != string::npos) reverse(word.begin(), word.begin() + i + 1);
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if (i != string::npos) {
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reverse(word.begin(), word.begin() + i + 1);
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}
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return word;
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}
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};
@@ -112,9 +130,11 @@ func reversePrefix(word string, ch byte) string {
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```ts
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function reversePrefix(word: string, ch: string): string {
115-
let idx = word.indexOf(ch) + 1;
116-
if (!idx) return word;
117-
return [...word.substring(0, idx)].reverse().join('') + word.substring(idx);
133+
const i = word.indexOf(ch) + 1;
134+
if (!i) {
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return word;
136+
}
137+
return [...word.slice(0, i)].reverse().join('') + word.slice(i);
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}
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```
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‎solution/2000-2099/2000.Reverse Prefix of Word/Solution.cpp

+3-1
Original file line numberDiff line numberDiff line change
@@ -2,7 +2,9 @@ class Solution {
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public:
33
string reversePrefix(string word, char ch) {
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int i = word.find(ch);
5-
if (i != string::npos) reverse(word.begin(), word.begin() + i + 1);
5+
if (i != string::npos) {
6+
reverse(word.begin(), word.begin() + i + 1);
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}
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return word;
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}
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};

‎solution/2000-2099/2000.Reverse Prefix of Word/Solution.java

+11-6
Original file line numberDiff line numberDiff line change
@@ -1,10 +1,15 @@
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class Solution {
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public String reversePrefix(String word, char ch) {
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int i = word.indexOf(ch);
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return i == -1 ? word
5-
: new StringBuilder(word.substring(0, i + 1))
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.reverse()
7-
.append(word.substring(i + 1))
8-
.toString();
3+
int j = word.indexOf(ch);
4+
if (j == -1) {
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return word;
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}
7+
char[] cs = word.toCharArray();
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for (int i = 0; i < j; ++i, --j) {
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char t = cs[i];
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cs[i] = cs[j];
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cs[j] = t;
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}
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return String.valueOf(cs);
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}
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}

‎solution/2000-2099/2000.Reverse Prefix of Word/Solution.ts

+5-3
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,7 @@
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function reversePrefix(word: string, ch: string): string {
2-
let idx = word.indexOf(ch) + 1;
3-
if (!idx) return word;
4-
return [...word.substring(0, idx)].reverse().join('') + word.substring(idx);
2+
const i = word.indexOf(ch) + 1;
3+
if (!i) {
4+
return word;
5+
}
6+
return [...word.slice(0, i)].reverse().join('') + word.slice(i);
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}

‎solution/2000-2099/2001.Number of Pairs of Interchangeable Rectangles/README.md

+29
Original file line numberDiff line numberDiff line change
@@ -153,6 +153,35 @@ func gcd(a, b int) int {
153153
}
154154
```
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156+
### **JavaScript**
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```js
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/**
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* @param {number[][]} rectangles
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* @return {number}
162+
*/
163+
var interchangeableRectangles = function (rectangles) {
164+
const cnt = new Map();
165+
let ans = 0;
166+
for (let [w, h] of rectangles) {
167+
const g = gcd(w, h);
168+
w = Math.floor(w / g);
169+
h = Math.floor(h / g);
170+
const x = w * (rectangles.length + 1) + h;
171+
ans += cnt.get(x) | 0;
172+
cnt.set(x, (cnt.get(x) | 0) + 1);
173+
}
174+
return ans;
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};
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177+
function gcd(a, b) {
178+
if (b == 0) {
179+
return a;
180+
}
181+
return gcd(b, a % b);
182+
}
183+
```
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156185
### **...**
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158187
```

‎solution/2000-2099/2001.Number of Pairs of Interchangeable Rectangles/README_EN.md

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@@ -137,6 +137,35 @@ func gcd(a, b int) int {
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}
138138
```
139139

140+
### **JavaScript**
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```js
143+
/**
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* @param {number[][]} rectangles
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* @return {number}
146+
*/
147+
var interchangeableRectangles = function (rectangles) {
148+
const cnt = new Map();
149+
let ans = 0;
150+
for (let [w, h] of rectangles) {
151+
const g = gcd(w, h);
152+
w = Math.floor(w / g);
153+
h = Math.floor(h / g);
154+
const x = w * (rectangles.length + 1) + h;
155+
ans += cnt.get(x) | 0;
156+
cnt.set(x, (cnt.get(x) | 0) + 1);
157+
}
158+
return ans;
159+
};
160+
161+
function gcd(a, b) {
162+
if (b == 0) {
163+
return a;
164+
}
165+
return gcd(b, a % b);
166+
}
167+
```
168+
140169
### **...**
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142171
```

‎solution/2000-2099/2001.Number of Pairs of Interchangeable Rectangles/Solution.js

+24
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,24 @@
1+
/**
2+
* @param {number[][]} rectangles
3+
* @return {number}
4+
*/
5+
var interchangeableRectangles = function (rectangles) {
6+
const cnt = new Map();
7+
let ans = 0;
8+
for (let [w, h] of rectangles) {
9+
const g = gcd(w, h);
10+
w = Math.floor(w / g);
11+
h = Math.floor(h / g);
12+
const x = w * (rectangles.length + 1) + h;
13+
ans += cnt.get(x) | 0;
14+
cnt.set(x, (cnt.get(x) | 0) + 1);
15+
}
16+
return ans;
17+
};
18+
19+
function gcd(a, b) {
20+
if (b == 0) {
21+
return a;
22+
}
23+
return gcd(b, a % b);
24+
}

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