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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
public bool IsPerfectSquare(int num) { if(num == 0 || num == 1) return true; /*if(num == Int32.MaxValue) return false; int i = 0; int square = 0; while(square<=num) { square = i*i; if(num == square) return true; i++; } return false;*/ for (int i = 1; i <= num / i; ++i) { if (i * i == num) return true; } return false; }
public bool IsPerfectSquare(int num) { if(num == 0 || num == 1) return true; //if(num == Int32.MaxValue) return false; long a = num/2; long square = a*a; while(square > num) { a = a/2; square = a*a; } for(long i = a;i<=a*2;i++) { if(i*i == num) return true; } return false; }
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原文地址：http://www.cnblogs.com/renyualbert/p/5874202.html
