Sqrt(x)——LeetCode

Implement int sqrt(int x).

Compute and return the square root of x.

题目大意：实现求一个int的根。

解题思路：二分。

public class Solution {
    public int mySqrt(int x) {
        if (x <= 0) {
            return 0;
        }
        if (x <= 3) {
            return 1;
        }
        long num = x / 2;
        int tmp = x;
        while (num * num >= tmp) {
            if (x / 2 == 0) {
                break;
            }
            num = x / 2;
            x /= 2;
        }
        long low = num, high = num * 2, mid = 0;
        while (low <= high) {
            mid = (low + high) >> 1;
            if (mid * mid <= tmp && (mid + 1) * (mid + 1) > tmp) {
                break;
            } else if (mid * mid > tmp) {
                high = mid - 1;
            } else {
                low = mid + 1;
            }
        }
        return (int) mid;
    }
}