Leetcode:valid Perfect Square

Valid Perfect Square


Total Accepted: 1976 Total Submissions: 5317 Difficulty: Medium

Given a positive integer num, write a function which returns True if num is a perfect square else False.

Note: do not use any built-in library function such as sqrt .

Example 1:

Input:16returns:true

Example 2:

Input:14returns:false

Credits:
Special thanks to @elmirap for adding this problem and creating all test cases.

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Ideas:

Two-point lookup.

Java code:

public class Solution {public    boolean isperfectsquare (int num) {                long lo = 1, hi = NUM/2;                if (num = = 1) return true;                long x = num;                while (lo <= hi) {            long mid = lo + (Hi-lo)/2;            if (mid * mid = = = x)                return true;            else if (Mid * mid < x)                lo = mid + 1;            else                hi = mid-1;        }        return false;    }}

Leetcode:valid Perfect Square