Easy

Simple two pinters记住只需要遍历到sqrt(c)就可以了.

class Solution {
    public boolean judgeSquareSum(int c) {
        int i = 0;
        int j = (int) Math.sqrt(c);
        while (i <= j){
            int squareSum = i*i + j*j;
            if (squareSum == c){
                return true;
            } else if (squareSum > c){
                j--;
            } else {
                i++;
            }
        }
        return false;
    }
}