633. Sum of Square Numbers

Given a non-negative integer c, your task is to decide whether there're two integers a and b such that a2 + b2 = c.

Example 1:

Input: 5
Output: True
Explanation: 1 * 1 + 2 * 2 = 5

Example 2:

Input: 3
Output: False


判断c是否为a^2+b^2

C++(3ms):

class Solution {
public:
    bool judgeSquareSum(int c) {
        int left = 0 ;
        int right = (int)sqrt(c) ;
        while(left <= right){
            int cur = left*left + right*right ;
            if (cur == c){
                return true ;
            }else if (cur < c){
                left++ ;
            }else{
                right-- ;
            }
        }
        return false ;
    }
};

java(14ms):

class Solution {
    public boolean judgeSquareSum(int c) {
        int left = 0 ;
        int right = (int)Math.sqrt(c) ;
        while(left <= right){
            int cur = left*left + right*right ;
            if (cur == c){
                return true ;
            }else if (cur < c){
                left++ ;
            }else{
                right-- ;
            }
        }
        return false ;
    }
}