feat: add solutions to lc problem: No.0043

No.0043.Multiply Strings

Author: yanglbme

solution/0000-0099/0043.Multiply Strings/README.md

@@ -39,15 +39,79 @@
 <!-- 这里可写当前语言的特殊实现逻辑 -->
 
 ```python
-
+class Solution:
+    def multiply(self, num1: str, num2: str) -> str:
+        def add(s1, s2):
+            n1, n2 = len(s1), len(s2)
+            i = carry = 0
+            res = []
+            while i < max(n1, n2) or carry > 0:
+                a = int(s1[n1 - i - 1]) if i < n1 else 0
+                b = int(s2[n2 - i - 1]) if i < n2 else 0
+                carry, t = divmod(a + b + carry, 10)
+                res.append(str(t))
+                i += 1
+            return ''.join(res[::-1])
+        
+        if '0' in [num1, num2]:
+            return '0'
+        n1, n2 = len(num1), len(num2)
+        ans = ''
+        for i in range(n1):
+            a = int(num1[n1 - i - 1])
+            t = ''
+            for j in range(n2):
+                b = int(num2[n2 - j - 1])
+                t = add(t, str(a * b) + '0' * j)
+            ans = add(ans, t + '0' * i)
+        return ans
 ```
 
 ### **Java**
 
 <!-- 这里可写当前语言的特殊实现逻辑 -->
 
 ```java
+class Solution {
+    public String multiply(String num1, String num2) {
+        if (Objects.equals(num1, "0") || Objects.equals(num2, "0")) {
+            return "0";
+        }
+        int n1 = num1.length(), n2 = num2.length();
+        String ans = "";
+        for (int i = 0; i < n1; ++i) {
+            int a = num1.charAt(n1 - i - 1) - '0';
+            String t = "";
+            for (int j = 0; j < n2; ++j) {
+                int b = num2.charAt(n2 - j - 1) - '0';
+                StringBuilder sb = new StringBuilder(String.valueOf(a * b));
+                for (int k = 0; k < j; ++k) {
+                    sb.append(0);
+                }
+                t = add(t, sb.toString());
+            }
+            StringBuilder sb = new StringBuilder(t);
+            for (int k = 0; k < i; ++k) {
+                sb.append(0);
+            }
+            ans = add(ans, sb.toString());
+        }
+        return ans;
+    }
 
+    private String add(String s1, String s2) {
+        int n1 = s1.length(), n2 = s2.length();
+        StringBuilder res = new StringBuilder();
+        for (int i = 0, carry = 0; i < Math.max(n1, n2) || carry > 0; ++i) {
+            int a = i < n1 ? (s1.charAt(n1 - i - 1) - '0') : 0;
+            int b = i < n2 ? (s2.charAt(n2 - i - 1) - '0') : 0;
+            int s = a + b + carry;
+            carry = s / 10;
+            res.append(s % 10);
+        }
+        return res.reverse().toString();
+    }
+}
 ```
 
 ### **TypeScript**
@@ -57,10 +121,10 @@ function multiply(num1: string, num2: string): string {
     if ([num1, num2].includes('0')) return '0';
     const n1 = num1.length, n2 = num2.length;
     let ans = '';
-    for(let i = 0; i < n1; i++) {
+    for (let i = 0; i < n1; i++) {
         let cur1 = parseInt(num1.charAt(n1 - i - 1), 10);
         let sum = '';
-        for(let j = 0; j < n2; j++) {
+        for (let j = 0; j < n2; j++) {
             let cur2 = parseInt(num2.charAt(n2 - j - 1), 10);
             sum = addString(sum, cur1 * cur2 + ('0'.repeat(j)));
         }
@@ -74,14 +138,14 @@ function addString(s1: string, s2: string): string {
     let ans = [];
     let sum = 0;
     for (let i = 0; i < n1 || i < n2 || sum > 0; i++) {
-        let num1 = s1.charAt(i) ? parseInt(s1.charAt(i), 10) : 0;
-        let num2 = s2.charAt(i) ? parseInt(s2.charAt(i), 10) : 0;
+        let num1 = i < n1 ? parseInt(s1.charAt(n1 - i - 1), 10) : 0;
+        let num2 = i < n2 ? parseInt(s2.charAt(n2 - i - 1), 10) : 0;
         sum += (num1 + num2);
         ans.unshift(sum % 10);
         sum = Math.floor(sum / 10);
     }
     return ans.join('');
-}
+};
 ```
 
 ### **...**

solution/0000-0099/0043.Multiply Strings/README_EN.md

@@ -25,21 +25,84 @@
 	<li>Both <code>num1</code> and <code>num2</code>&nbsp;do not contain any leading zero, except the number <code>0</code> itself.</li>
 </ul>
 
-
 ## Solutions
 
 <!-- tabs:start -->
 
 ### **Python3**
 
 ```python
-
+class Solution:
+    def multiply(self, num1: str, num2: str) -> str:
+        def add(s1, s2):
+            n1, n2 = len(s1), len(s2)
+            i = carry = 0
+            res = []
+            while i < max(n1, n2) or carry > 0:
+                a = int(s1[n1 - i - 1]) if i < n1 else 0
+                b = int(s2[n2 - i - 1]) if i < n2 else 0
+                carry, t = divmod(a + b + carry, 10)
+                res.append(str(t))
+                i += 1
+            return ''.join(res[::-1])
+        
+        if '0' in [num1, num2]:
+            return '0'
+        n1, n2 = len(num1), len(num2)
+        ans = ''
+        for i in range(n1):
+            a = int(num1[n1 - i - 1])
+            t = ''
+            for j in range(n2):
+                b = int(num2[n2 - j - 1])
+                t = add(t, str(a * b) + '0' * j)
+            ans = add(ans, t + '0' * i)
+        return ans
 ```
 
 ### **Java**
 
 ```java
+class Solution {
+    public String multiply(String num1, String num2) {
+        if (Objects.equals(num1, "0") || Objects.equals(num2, "0")) {
+            return "0";
+        }
+        int n1 = num1.length(), n2 = num2.length();
+        String ans = "";
+        for (int i = 0; i < n1; ++i) {
+            int a = num1.charAt(n1 - i - 1) - '0';
+            String t = "";
+            for (int j = 0; j < n2; ++j) {
+                int b = num2.charAt(n2 - j - 1) - '0';
+                StringBuilder sb = new StringBuilder(String.valueOf(a * b));
+                for (int k = 0; k < j; ++k) {
+                    sb.append(0);
+                }
+                t = add(t, sb.toString());
+            }
+            StringBuilder sb = new StringBuilder(t);
+            for (int k = 0; k < i; ++k) {
+                sb.append(0);
+            }
+            ans = add(ans, sb.toString());
+        }
+        return ans;
+    }
 
+    private String add(String s1, String s2) {
+        int n1 = s1.length(), n2 = s2.length();
+        StringBuilder res = new StringBuilder();
+        for (int i = 0, carry = 0; i < Math.max(n1, n2) || carry > 0; ++i) {
+            int a = i < n1 ? (s1.charAt(n1 - i - 1) - '0') : 0;
+            int b = i < n2 ? (s2.charAt(n2 - i - 1) - '0') : 0;
+            int s = a + b + carry;
+            carry = s / 10;
+            res.append(s % 10);
+        }
+        return res.reverse().toString();
+    }
+}
 ```
 
 ### **TypeScript**
@@ -49,10 +112,10 @@ function multiply(num1: string, num2: string): string {
     if ([num1, num2].includes('0')) return '0';
     const n1 = num1.length, n2 = num2.length;
     let ans = '';
-    for(let i = 0; i < n1; i++) {
+    for (let i = 0; i < n1; i++) {
         let cur1 = parseInt(num1.charAt(n1 - i - 1), 10);
         let sum = '';
-        for(let j = 0; j < n2; j++) {
+        for (let j = 0; j < n2; j++) {
             let cur2 = parseInt(num2.charAt(n2 - j - 1), 10);
             sum = addString(sum, cur1 * cur2 + ('0'.repeat(j)));
         }
@@ -66,14 +129,14 @@ function addString(s1: string, s2: string): string {
     let ans = [];
     let sum = 0;
     for (let i = 0; i < n1 || i < n2 || sum > 0; i++) {
-        let num1 = s1.charAt(i) ? parseInt(s1.charAt(i), 10) : 0;
-        let num2 = s2.charAt(i) ? parseInt(s2.charAt(i), 10) : 0;
+        let num1 = i < n1 ? parseInt(s1.charAt(n1 - i - 1), 10) : 0;
+        let num2 = i < n2 ? parseInt(s2.charAt(n2 - i - 1), 10) : 0;
         sum += (num1 + num2);
         ans.unshift(sum % 10);
         sum = Math.floor(sum / 10);
     }
     return ans.join('');
-}
+};
 ```
 
 ### **...**

solution/0000-0099/0043.Multiply Strings/Solution.java

@@ -1,28 +1,40 @@
 class Solution {
     public String multiply(String num1, String num2) {
-        char[] chars1 = num1.toCharArray(),chars2 = num2.toCharArray();
-        int[] result = new int[chars1.length+chars2.length];
-        int pow = result.length-1;
-        for (int i = chars1.length - 1; i >= 0; i--) {
-            int a = chars1[i] - '0';
-            int j = 0,bit = pow;
-            for (int i1 = chars2.length - 1; i1 >= 0; i1--) {
-                int b = chars2[i1] -'0';
-                j = a*b + j + result[bit];
-                result[bit--] = j%10;
-                j = j/10;
+        if (Objects.equals(num1, "0") || Objects.equals(num2, "0")) {
+            return "0";
+        }
+        int n1 = num1.length(), n2 = num2.length();
+        String ans = "";
+        for (int i = 0; i < n1; ++i) {
+            int a = num1.charAt(n1 - i - 1) - '0';
+            String t = "";
+            for (int j = 0; j < n2; ++j) {
+                int b = num2.charAt(n2 - j - 1) - '0';
+                StringBuilder sb = new StringBuilder(String.valueOf(a * b));
+                for (int k = 0; k < j; ++k) {
+                    sb.append(0);
+                }
+                t = add(t, sb.toString());
             }
-            while (j!=0){
-                j += result[bit];
-                result[bit--] = j%10;
-                j = j/10;
+            StringBuilder sb = new StringBuilder(t);
+            for (int k = 0; k < i; ++k) {
+                sb.append(0);
             }
-            pow--;
+            ans = add(ans, sb.toString());
+        }
+        return ans;
+    }
+
+    private String add(String s1, String s2) {
+        int n1 = s1.length(), n2 = s2.length();
+        StringBuilder res = new StringBuilder();
+        for (int i = 0, carry = 0; i < Math.max(n1, n2) || carry > 0; ++i) {
+            int a = i < n1 ? (s1.charAt(n1 - i - 1) - '0') : 0;
+            int b = i < n2 ? (s2.charAt(n2 - i - 1) - '0') : 0;
+            int s = a + b + carry;
+            carry = s / 10;
+            res.append(s % 10);
         }
-        StringBuilder builder = new StringBuilder();
-        int i = 0;
-        for (; i < result.length; i++) if (result[i] != 0) break;
-        for (; i < result.length; i++) builder.append(result[i]);
-        return builder.length()==0? "0" : builder.toString();
+        return res.reverse().toString();
     }
 }

solution/0000-0099/0043.Multiply Strings/Solution.py

@@ -1,20 +1,26 @@
-class Solution(object):
-    def multiply(self, num1, num2):
+class Solution:
+    def multiply(self, num1: str, num2: str) -> str:
+        def add(s1, s2):
+            n1, n2 = len(s1), len(s2)
+            i = carry = 0
+            res = []
+            while i < max(n1, n2) or carry > 0:
+                a = int(s1[n1 - i - 1]) if i < n1 else 0
+                b = int(s2[n2 - i - 1]) if i < n2 else 0
+                carry, t = divmod(a + b + carry, 10)
+                res.append(str(t))
+                i += 1
+            return ''.join(res[::-1])
 
-        # Create a dictionary to store 0-9 key-value pairs
-        dict_nums={"0": 0, "1": 1, "2": 2, "3": 3, "4": 4, "5": 5, "6": 6, "7": 7, "8": 8, "9": 9}
-        number1 = 0
-        number2 = 0
-
-	# Convert num1 in integer format
-        for i in num1:
-            key = dict_nums[i]
-            number1 = (number1 * 10) + key
-
-
-	# Convert num2 in integer format
-        for i in num2:
-	    key = dict_nums[i]
-		number2 = (number2 * 10) + key
-
-        return str(number1 * number2)
+        if '0' in [num1, num2]:
+            return '0'
+        n1, n2 = len(num1), len(num2)
+        ans = ''
+        for i in range(n1):
+            a = int(num1[n1 - i - 1])
+            t = ''
+            for j in range(n2):
+                b = int(num2[n2 - j - 1])
+                t = add(t, str(a * b) + '0' * j)
+            ans = add(ans, t + '0' * i)
+        return ans

solution/0000-0099/0043.Multiply Strings/Solution.ts

@@ -2,10 +2,10 @@ function multiply(num1: string, num2: string): string {
     if ([num1, num2].includes('0')) return '0';
     const n1 = num1.length, n2 = num2.length;
     let ans = '';
-    for(let i = 0; i < n1; i++) {
+    for (let i = 0; i < n1; i++) {
         let cur1 = parseInt(num1.charAt(n1 - i - 1), 10);
         let sum = '';
-        for(let j = 0; j < n2; j++) {
+        for (let j = 0; j < n2; j++) {
             let cur2 = parseInt(num2.charAt(n2 - j - 1), 10);
             sum = addString(sum, cur1 * cur2 + ('0'.repeat(j)));
         }
@@ -19,11 +19,11 @@ function addString(s1: string, s2: string): string {
     let ans = [];
     let sum = 0;
     for (let i = 0; i < n1 || i < n2 || sum > 0; i++) {
-        let num1 = s1.charAt(i) ? parseInt(s1.charAt(i), 10) : 0;
-        let num2 = s2.charAt(i) ? parseInt(s2.charAt(i), 10) : 0;
+        let num1 = i < n1 ? parseInt(s1.charAt(n1 - i - 1), 10) : 0;
+        let num2 = i < n2 ? parseInt(s2.charAt(n2 - i - 1), 10) : 0;
         sum += (num1 + num2);
         ans.unshift(sum % 10);
         sum = Math.floor(sum / 10);
     }
     return ans.join('');
-}
+};