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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: 16 Returns: True
Example 2:
Input: 14 Returns: False
Credits:
Special thanks to @elmirap for adding this problem and creating all test cases.
public class Solution { public boolean isPerfectSquare(int num) { long start = 0; long end = num/2; if(num==1)return true; while(start<=end) { long mid = (long)start + (end-start)/2; long val = (long)mid * mid; if(val==num) return true; else if(val<num) { start = mid+1; } else { end = mid-1; } } return false; } }
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原文地址：http://www.cnblogs.com/hygeia/p/5774930.html
