69. Sqrt(x)

题目分析

Implement int sqrt(int x).

Compute and return the square root of x.

x is guaranteed to be a non-negative integer.

Example 1:

Input: 4
Output: 2

Example 2:

Input: 8
Output: 2

Explanation: The square root of 8 is 2.82842..., and since we want to return an integer, the decimal part will be truncated.

这里采用二分法的方法来解这道题目。

代码

class Solution {
    public int mySqrt(int x) {
        if(x <= 0) return 0;
        int low = 1, high = x;
        while(low <= high) {
            long mid = (high - low) / 2 + low;
            if(mid * mid == x) {
                return (int)mid;
            } else if(mid * mid < x) {
                low = (int)mid + 1;
            } else {
                high = (int)mid - 1;
            }
        }
        return low - 1;
    }
}