complete 43 big data multiply and 415 big data add by python

Author: bbruceyuan

README.md

@@ -1,9 +1,9 @@
 # Keep thinking, keep alive
-Until 2018-01-25 19:54:00, I have solved **63** / **686** problems while **126** are still locked.
+Until 2018-01-27 14:23:21, I have solved **65** / **686** problems while **126** are still locked.
 
 Completion statistic: 
 1. JavaScript: 59 
-2. Python: 6
+2. Python: 8
 3. C++: 1
 4. Java: 1
 
@@ -55,7 +55,7 @@ Note: :lock: means you need to buy a book from LeetCode
 |040|[Combination Sum II](https://leetcode.com/problems/combination-sum-ii/description/) |Medium|[JavaScript](https://github.com/hey-bruce/algorithms_and_oj/blob/master/leetcode-algorithms/040.%20Combination%20Sum%20II/combinationSumTwo.js)|To Do|To Do|To Do|
 |041|[First Missing Positive](https://leetcode.com/problems/first-missing-positive/description/) |Hard|[JavaScript](https://github.com/hey-bruce/algorithms_and_oj/blob/master/leetcode-algorithms/041.%20First%20Missing%20Positive/firstMissingPositive.js)|To Do|To Do|To Do|
 |042|[Trapping Rain Water](https://leetcode.com/problems/trapping-rain-water/description/) |Hard|To Do|To Do|To Do|To Do|
-|043|[Multiply Strings](https://leetcode.com/problems/multiply-strings/description/) |Medium|To Do|To Do|To Do|To Do|
+|043|[Multiply Strings](https://leetcode.com/problems/multiply-strings/description/) |Medium|To Do|[Python](https://github.com/hey-bruce/algorithms_and_oj/blob/master/leetcode-algorithms/043.%20Multiply%20Strings/solution.py)|To Do|To Do|
 |044|[Wildcard Matching](https://leetcode.com/problems/wildcard-matching/description/) |Hard|To Do|To Do|To Do|To Do|
 |045|[Jump Game II](https://leetcode.com/problems/jump-game-ii/description/) |Hard|To Do|To Do|To Do|To Do|
 |046|[Permutations](https://leetcode.com/problems/permutations/description/) |Medium|To Do|To Do|To Do|To Do|
@@ -410,7 +410,7 @@ Note: :lock: means you need to buy a book from LeetCode
 |412|[Fizz Buzz](https://leetcode.com/problems/fizz-buzz/description/) |Easy|To Do|To Do|To Do|To Do|
 |413|[Arithmetic Slices](https://leetcode.com/problems/arithmetic-slices/description/) |Medium|To Do|To Do|To Do|To Do|
 |414|[Third Maximum Number](https://leetcode.com/problems/third-maximum-number/description/) |Easy|[JavaScript](https://github.com/hey-bruce/algorithms_and_oj/blob/master/leetcode-algorithms/414.%20Third%20Maximum%20Number/thirdMax.js)|To Do|To Do|To Do|
-|415|[Add Strings](https://leetcode.com/problems/add-strings/description/) |Easy|To Do|To Do|To Do|To Do|
+|415|[Add Strings](https://leetcode.com/problems/add-strings/description/) |Easy|To Do|[Python](https://github.com/hey-bruce/algorithms_and_oj/blob/master/leetcode-algorithms/415.%20Add%20Strings/solution.py)|To Do|To Do|
 |416|[Partition Equal Subset Sum](https://leetcode.com/problems/partition-equal-subset-sum/description/) |Medium|To Do|To Do|To Do|To Do|
 |417|[Pacific Atlantic Water Flow](https://leetcode.com/problems/pacific-atlantic-water-flow/description/) |Medium|To Do|To Do|To Do|To Do|
 |418|[Sentence Screen Fitting](https://leetcode.com/problems/sentence-screen-fitting/description/) :lock:|Medium|To Do|To Do|To Do|To Do|

leetcode-algorithms/043. Multiply Strings/solution.py

@@ -0,0 +1,48 @@
+#!/usr/bin/env python
+# Created by Bruce yuan on 18-1-27.
+
+
+class Solution:
+    def multiply(self, num1, num2):
+        """
+        :type num1: str
+        :type num2: str
+        :rtype: str
+        """
+        # 因为题目说了不会用 0 开头，所以　０　开头一定是　０
+        if num1[0] == '0' or num2[0] == '0':
+            return '0'
+        # 用一个数组来表示结果
+        result = [0] * (len(num1) + len(num2))
+        cur_pos = len(result) - 1
+
+        for first_str in reversed(num1):
+            # 第一个乘数
+            int1 = int(first_str)
+            tmp_pos = cur_pos
+            carry = 0
+            for second_str in reversed(num2):
+                # 第二个乘数
+                int2 = int(second_str)
+                tmp_result = int1 * int2
+                # 返回进位和当前位置的数字，因为两个数相乘最多等于 81
+                result[tmp_pos] += tmp_result
+                result[tmp_pos - 1] += result[tmp_pos] // 10
+                result[tmp_pos] = result[tmp_pos] % 10
+                # print(result)
+                tmp_pos -= 1
+            cur_pos -= 1
+        for index, item in enumerate(result):
+            if item != 0:
+                pos = index
+                break
+        return ''.join(str(item) for item in result[pos:])
+
+
+def main():
+    a = Solution()
+    result = a.multiply('999', '999')
+    print(result)
+
+if __name__ == '__main__':
+    main()

leetcode-algorithms/415. Add Strings/solution.py

@@ -0,0 +1,23 @@
+#!/usr/bin/env python
+# Created by Bruce yuan on 18-1-27.
+
+
+class Solution:
+    def addStrings(self, num1, num2):
+        """
+        :type num1: str
+        :type num2: str
+        :rtype: str
+        """
+        carry = 0
+        result = []
+        num1, num2 = list(num1), list(num2)
+        while len(num2) > 0 or len(num1) > 0:
+            n1 = int(num1.pop()) if len(num1) > 0 else 0
+            n2 = int(num2.pop()) if len(num2) > 0 else 0
+            tmp = n1 + n2 + carry
+            result.append(tmp % 10)
+            carry = tmp // 10
+        if carry == 0:
+            result.append(carry)
+        return ''.join(str(x) for x in result[::-1])