/*
 * @lc app=leetcode id=367 lang=java
 *
 * [367] Valid Perfect Square
 */

// @lc code=start
class Solution {
    public boolean isPerfectSquare(int num) {
        long i = 0, j = num, m;
        while(i <= j) {
            m = i + (j-i)/2;
            if(m * m == num) {
                return true;
            } else if(m * m <num) {
                i = m + 1;
            } else {
                j = m - 1;
            }
        }
        return false;
    }
}
// @lc code=end