<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) {
        int half = c >> 1;
        long long xs[100010];
        int tt = -1;
        for (int a = 0; a <= sqrt(c+1); a++)
        {
        
            xs[++tt]= (long long)a*a;
        }
        for (int l = 0, r = tt; r >= l; r--)
        {
            while (l <= r&& l + 1<= r && xs[l+1] + xs[r] <= c) l++;
            // cout << xs[l ] << "," <<xs[r] <<endl;
            if (c == xs[l] + xs[r]) return true;
        }
        return false;
    }
};
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