题解 | #求平方根#

import java.util.*;


public class Solution {
    /**
     * 
     * @param x int整型 
     * @return int整型
     */
    public int mysqrt (int x) {
        // write code here
        if (x < 0) {
            throw new IllegalArgumentException("param must be positive");
        } 
        if (x == 0) {
            return 0;
        }
        long l = 1;
        long r = x;
        long mid;
        while (l < r) {
            mid = l + (r - l) / 2;
            if (mid * mid <= x && (mid + 1) * (mid + 1) > x) {
                return (int) mid;
            } else if (mid * mid < x) {
                l = mid + 1;
            } else {
                r = mid - 1;
            }
        }
        return (int) l;
    }
}