[leetcode]69. Sqrt(x)开方

Implement int sqrt(int x).

Compute and return the square root of x, where x is guaranteed to be a non-negative integer.

Since the return type is an integer, the decimal digits are truncated and only the integer part of the result is returned.

Example 1:

Input: 4
Output: 2

Example 2:

Input: 8
Output: 2
Explanation: The square root of 8 is 2.82842..., and since 
             the decimal part is truncated, 2 is returned.

题意：

整数开方

Solution1： Binary Search

code

 1 class Solution {
 2     public int mySqrt(int x) {
 3         if ( x == 0 ) return 0;
 4         int left = 1;
 5         int right = x;
 6         int result = 0;
 7             
 8         while (left <= right) {
 9             int mid = left + (right - left) / 2;
10             if (mid <= x / mid) {
11                 left = mid + 1;
12                 result = mid;
13             } else {
14                 right = mid - 1;
15             }
16         }
17         return result;    
18     }
19 }