feat: add solutions to lc problem: No.0043

No.0043.Multiply Strings

Author: YangFong

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

@@ -156,6 +156,66 @@ function addString(s1: string, s2: string): string {
 }
 ```
 
+```ts
+function multiply(num1: string, num2: string): string {
+    const res = ['0'];
+    if (num1 === '0' || num2 === '0') {
+        return res.join('');
+    }
+
+    const n = num1.length;
+    const m = num2.length;
+    for (let i = 0; i < n; i++) {
+        const num = Number(num1[n - 1 - i]);
+        let sum = 0;
+        for (let j = 0; j < m || sum != 0; j++) {
+            sum +=
+                (Number(num2[m - 1 - j]) || 0) * num +
+                (Number(res[i + j]) || 0);
+            res[i + j] = `${sum % 10}`;
+            sum = Math.floor(sum / 10);
+        }
+    }
+
+    return res.reverse().join('');
+}
+```
+
+### **Rust**
+
+```rust
+impl Solution {
+    pub fn multiply(num1: String, num2: String) -> String {
+        if num1 == "0" || num2 == "0" {
+            return String::from("0");
+        }
+        let mut res = vec![0];
+        let num1 = num1.as_bytes();
+        let num2 = num2.as_bytes();
+        let n = num1.len();
+        let m = num2.len();
+        for i in 0..n {
+            let num = num1[n - i - 1] - b'0';
+            let mut sum = 0;
+            let mut j = 0;
+            while j < m || sum != 0 {
+                if i + j == res.len() {
+                    res.push(0);
+                }
+                sum += num * (num2.get(m - j - 1).unwrap_or(&b'0') - b'0') + res[i + j];
+                res[i + j] = sum % 10;
+                sum /= 10;
+                j += 1;
+            }
+        }
+        res.iter()
+            .rev()
+            .map(|num| num.to_string())
+            .collect::<String>()
+    }
+}
+```
+
 ### **...**
 
 ```

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

@@ -141,6 +141,66 @@ function addString(s1: string, s2: string): string {
 }
 ```
 
+```ts
+function multiply(num1: string, num2: string): string {
+    const res = ['0'];
+    if (num1 === '0' || num2 === '0') {
+        return res.join('');
+    }
+
+    const n = num1.length;
+    const m = num2.length;
+    for (let i = 0; i < n; i++) {
+        const num = Number(num1[n - 1 - i]);
+        let sum = 0;
+        for (let j = 0; j < m || sum != 0; j++) {
+            sum +=
+                (Number(num2[m - 1 - j]) || 0) * num +
+                (Number(res[i + j]) || 0);
+            res[i + j] = `${sum % 10}`;
+            sum = Math.floor(sum / 10);
+        }
+    }
+
+    return res.reverse().join('');
+}
+```
+
+### **Rust**
+
+```rust
+impl Solution {
+    pub fn multiply(num1: String, num2: String) -> String {
+        if num1 == "0" || num2 == "0" {
+            return String::from("0");
+        }
+        let mut res = vec![0];
+        let num1 = num1.as_bytes();
+        let num2 = num2.as_bytes();
+        let n = num1.len();
+        let m = num2.len();
+        for i in 0..n {
+            let num = num1[n - i - 1] - b'0';
+            let mut sum = 0;
+            let mut j = 0;
+            while j < m || sum != 0 {
+                if i + j == res.len() {
+                    res.push(0);
+                }
+                sum += num * (num2.get(m - j - 1).unwrap_or(&b'0') - b'0') + res[i + j];
+                res[i + j] = sum % 10;
+                sum /= 10;
+                j += 1;
+            }
+        }
+        res.iter()
+            .rev()
+            .map(|num| num.to_string())
+            .collect::<String>()
+    }
+}
+```
+
 ### **...**
 
 ```

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

@@ -0,0 +1,30 @@
+impl Solution {
+    pub fn multiply(num1: String, num2: String) -> String {
+        if num1 == "0" || num2 == "0" {
+            return String::from("0");
+        }
+        let mut res = vec![0];
+        let num1 = num1.as_bytes();
+        let num2 = num2.as_bytes();
+        let n = num1.len();
+        let m = num2.len();
+        for i in 0..n {
+            let num = num1[n - i - 1] - b'0';
+            let mut sum = 0;
+            let mut j = 0;
+            while j < m || sum != 0 {
+                if i + j == res.len() {
+                    res.push(0);
+                }
+                sum += num * (num2.get(m - j - 1).unwrap_or(&b'0') - b'0') + res[i + j];
+                res[i + j] = sum % 10;
+                sum /= 10;
+                j += 1;
+            }
+        }
+        res.iter()
+            .rev()
+            .map(|num| num.to_string())
+            .collect::<String>()
+    }
+}