原题链接: https://oj.leetcode.com/problems/sqrtx/

public int sqrt(int x) {
    if (x < 0) return -1;
    if (x == 0) return 0;

    int low = 1;
    int high = x / 2 + 1;

    while (low <= high) {
        int mid = (low + high) / 2;

        if (mid <= x / mid && x / (mid + 1) < mid + 1) {
            return mid;
        } else if (mid < x / mid) {
            low = mid + 1;
        } else {
            high = mid - 1;
        }
    }

    return 0;
}

求平方根的方法还有 “牛顿迭代法求平方根”, “卡马克快速平方根”。