leetcode_Valid Perfect Square

[题目]
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
【解法】
二分查找，从1 – num/2，因为除了1和4，一个数的开平方肯定小于这个数的一半，过程中注意溢出，因为两个比较大的int型相乘，可能溢出，因此程序中使用了long long类型。
【代码】

#include<iostream>#include<math.h>using namespace std;bool isPerfectSquare(int num1){    long long num = (long long) num1;    if(num == 0 || num == 1 || num == 4)    return true;    int temp = num/2+1;    int left = 1;    int right = temp;    while(left <= right)    {        //打印过程        //cout<<"("<<left<<","<<right<<")"<<endl;        //long long防止溢出         long long mid = left + (right - left) / 2;        if(mid * mid == num) return true;        else if(mid * mid < num)        left = mid + 1;        else        right = mid - 1;    }    return false;}int main(void){    for(int i = 1;i <= 1024;i++)    {        if(isPerfectSquare(i))        cout<<isPerfectSquare(i)<<endl;    }    system("pause");    return 0;}