add 43

Author: luliyucoordinate

README.md

@@ -43,6 +43,7 @@ LeetCode
 |0039|[Combination Sum](https://leetcode.com/problems/combination-sum/) | c | [c++](./src/0039-Combination-Sum/0039.cpp) |[python](./src/0039-Combination-Sum/0039.py)|||Medium|
 |0040|[Combination Sum II](https://leetcode.com/problems/combination-sum-ii/) | c | [c++](./src/0040-Combination-Sum-II/0040.cpp) |[python](./src/0040-Combination-Sum-II/0040.py)|||Medium|
 |0041|[First Missing Positive](https://leetcode.com/problems/first-missing-positive/) | c | [c++](./src/0041-First-Missing-Positive/0041.cpp) |[python](./src/0041-First-Missing-Positive/0041.py)|||Hard|
+|0043|[Multiply Strings](https://leetcode.com/problems/multiply-strings/) | c | [c++](./src/0043-Multiply-Strings/0043.cpp) |[python](./src/0043-Multiply-Strings/0043.py)|||Medium|
 |0044|[Wildcard Matching](https://leetcode.com/problems/wildcard-matching/) | c | [c++](./src/0044-Wildcard-Matching/0044.cpp) |[python](./src/0044-Wildcard-Matching/0044.py)|||Hard|
 |0045|[Jump Game II](https://leetcode.com/problems/jump-game-ii/) | c | [c++](./src/0045-Jump-Game-II/0045.cpp) |[python](./src/0045-Jump-Game-II/0045.py)|||Hard|
 |0046|[Permutations](https://leetcode.com/problems/permutations/) | c | [c++](./src/0046-Permutations/0046.cpp) |[python](./src/0046-Permutations/0046.py)|||Medium|

src/0043-Multiply-Strings/0043.cpp

@@ -0,0 +1,27 @@
+#include <string>
+using namespace std;
+
+static int x = []() {std::ios::sync_with_stdio(false); cin.tie(0); return 0; }();
+class Solution 
+{
+public:
+    string multiply(string num1, string num2) 
+    {
+        int m = num1.size(), n = num2.size();
+        string res(m + n, '0');
+        for (int i = m - 1; i >= 0; i--) 
+        {
+            for (int j = n - 1; j >= 0; j--) 
+            {
+                int sum = (num1[i] - '0') * (num2[j] - '0') + (ans[i + j + 1] - '0');
+                res[i + j + 1] = sum % 10 + '0';
+                res[i + j] += sum / 10;
+            }
+        }
+        for (int i = 0; i < m + n; i++) 
+        {
+            if (res[i] != '0') return res.substr(i);
+        }
+        return "0";
+    }
+};

src/0043-Multiply-Strings/0043.py

@@ -0,0 +1,19 @@
+class Solution:
+    def multiply(self, num1, num2):
+        """
+        :type num1: str
+        :type num2: str
+        :rtype: str
+        """
+        num1_len, num2_len = len(num1), len(num2)
+        res = ['0'] * (num1_len + num2_len)
+        for i in range(num2_len-1, -1, -1):
+            for j in range(num1_len-1, -1, -1):
+                tmp = int(num1[j]) * int(num2[i]) + int(res[i + j + 1])
+                res[i + j + 1] = str(tmp%10)
+                res[i + j] = str(int(res[i+j]) + tmp // 10)
+                
+        for i in range(num1_len + num2_len):
+            if res[i] != '0':
+                return ''.join(res[i:])
+        return '0'