<p>Given a non-negative integer <code>c</code>, decide whether there&#39;re two integers <code>a</code> and <code>b</code> such that <code>a<sup>2</sup> + b<sup>2</sup> = c</code>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> c = 5
<strong>Output:</strong> true
<strong>Explanation:</strong> 1 * 1 + 2 * 2 = 5
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> c = 3
<strong>Output:</strong> false
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>0 &lt;= c &lt;= 2<sup>31</sup> - 1</code></li>
</ul>

class Solution {
public:
    bool judgeSquareSum(int c) {
         unordered_set<long long> intSet;
         for(long i=0;i*i<=c;i++){
            intSet.insert(i*i);
            if(intSet.find(c-(i*i))!=intSet.end())  return true;
         }

         return false;
    }
};
// class Solution {
// public:
//     bool judgeSquareSum(int c) {
//         long long a = 0;
//         long long b = (int) sqrt(c);
//         while (a <= b) {
//             long long sum = a * a + b * b;
//             if (sum == c) {
//                 return true;
//             } else if (sum < c) {
//                 a++;
//             } else {
//                 b--;
//             }
//         }
//         return false;
//     }
// };
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