[leetcode] problem 633 – sum of square numbers

public boolean (int c) {
    int a = 0; 
    int b = (int) Math.sqrt(c);

    while (a <= b) {
        int sum = a * a + b * b;

        if (sum < c)
            a++;
        else if (sum > c)
            b--;
        else
            return true;
    }

    return false;
}