二进制求和

yingl · yingl · commit 88319c39aa10 · 2016-08-04T14:28:09.000+08:00
diff --git a/add_binary.py b/add_binary.py
@@ -0,0 +1,28 @@
+# -*- coding: utf-8 -*-
+
+class Solution:
+    # @param {string} a a number
+    # @param {string} b a number
+    # @return {string} the result
+    def addBinary(self, a, b):
+        # Write your code here
+        flag = 0
+        ret = ''
+        a_i, b_i = len(a) - 1, len(b) - 1
+        while (a_i >= 0) and (b_i >= 0):
+            va, vb = int(a[a_i]), int(b[b_i])
+            ret += str((va + vb + flag) % 2)
+            flag = (va + vb + flag) / 2
+            a_i -= 1
+            b_i -= 1
+        c_i = -1
+        if (a_i >= 0) or (b_i >= 0):
+            c = a if a_i >= 0 else b
+            c_i = a_i if a_i >= 0 else b_i
+        while c_i >= 0:
+            ret += str((int(c[c_i]) + flag) % 2)
+            flag = (int(c[c_i]) + flag) / 2
+            c_i -= 1
+        if flag:
+            ret += str(flag)
+        return ret[::-1]  # Python没有提供直接反转字符串的函数，用切片凑合一下吧。
