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069_sqrtx.py

@@ -0,0 +1,38 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+#@author: rye
+#@time: 2019/3/19
+
+'''
+二分法。
+当时没想到。
+tips：
+    注意return的条件
+'''
+class Solution(object):
+    def mySqrt(self, x):
+        """
+        :type x: int
+        :rtype: int
+        """
+        # 作弊
+        # return int(x ** (1 / 2))
+
+        if x == 0:
+            return 0
+        if x == 1:
+            return 1
+        l, r = 0, x - 1
+        while l <= r:
+            # mid1 = l + (r - l) >> 1
+            mid = l + ((r - l) >> 1)
+            if mid ** 2 <= x and (mid + 1) ** 2 > x:
+                return mid
+            elif mid ** 2 > x:
+                r = mid - 1
+            else:
+                l = mid + 1
+
+if __name__ == '__main__':
+    x = 3
+    print(Solution().mySqrt(x))