力扣-367.有效的完全平方数

暴力 class Solution { public: bool isPerfectSquare(int num) { for(long i = 1; i * i <= num; i++) { if(i * i == num) return true; } return false; } }; 二分查找 class Solution { public: bool isPerfectSquare(int num) { int left = 1, right = num; while(left <= right) { int mid = left + (right - left) / 2; long tmp = mid * mid; if(tmp == num) return true; else if(tmp < num) left = mid + 1; else right = mid - 1; } return false; } };