Problem

Implement int sqrt(int x).

Compute and return the square root of x.

Example
sqrt(3) = 1

sqrt(4) = 2

sqrt(5) = 2

sqrt(10) = 3

思路

二分, 注意 乘法精度问题

    public int sqrt(int x) {
        long start = 1;
        long end = x;
        while (start + 1 < end) {
            long mid = start + (end - start) / 2;
            long value = mid * mid;
            if (value < x) {
                start = mid;
            } else if (value > x) {
                end = mid;
            } else {
                return (int)mid;
            }
        }
        if (end * end <= x) return (int)end;
        return (int)start;
    }