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POAlgorithm to add sum of every possible xor-sum sub-array
 

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    <p>I participated in one algorithmic competition. I got stuck in one problem, I am asking the same here.</p> <p><strong>Problem Statement</strong></p> <p>XOR-sum array is to XOR all the numbers of that sub-array. An array is given to you, you have to add all possible such XOR-sub-array.</p> <p>For better understanding, question statement is <a href="http://www.codechef.com/COOK39/problems/PPXOR" rel="nofollow">here</a> also.</p> <p><strong>Example</strong></p> <p><strong>Input</strong></p> <p>Array :- 1 2</p> <p><strong>Output</strong> :- 6</p> <p><strong>Explanation</strong></p> <p><code>F(1, 1) = A[1] = 1</code>, <code>F(2, 2) = A[2] = 2</code> and <code>F(1, 2) = A[1] XOR A[2] = 1 XOR 2 = 3.</code></p> <p>Hence the answer is 1 + 2 + 3 = 6.</p> <p><strong>My code</strong></p> <p>Time Complexity :- O(N^2), (Inefficient one, didn't accpted in the competition)</p> <pre><code>#include&lt;iostream&gt; using namespace std; long long int input[100001]; main() { int T; int N; long long int val; long long int temp = 0; long long int answer = 0; cin &gt;&gt; T; while(T--) { cin &gt;&gt; N; for(int i = 0; i &lt; N; i++) { cin &gt;&gt; val; temp = temp^val; answer += temp; input[i] = temp; } for( int i = 0; i &lt; N; i++ ) { for( int j = i+1; j &lt; N; j++ ) { answer += input[i]^input[j]; } } cout &lt;&lt; answer &lt;&lt; endl; answer = 0; temp = 0; } return 0; } </code></pre> <p><strong>Question:-</strong></p> <p>I saw the best solution of this problem on <a href="http://www.codechef.com/viewplaintext/2928504" rel="nofollow">this link</a></p> <p>But in this code, I didn't understand below module, please help me to understand that.</p> <pre><code>for (int i=0, p=1; i&lt;30; i++, p&lt;&lt;=1) { int c=0; for (int j=0; j&lt;=N; j++) { if (A[j]&amp;p) c++; } ret+=(long long)c*(N-c+1)*p; } </code></pre> <p>Thanks in advance. Looking for your kind reply.</p>
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    1. COI think your talking about combinations with replacement, not every possible subarray, that would be a powerset
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    2. COI'm not sure but I think in this problem you will have to make use of the property that a^b = a + b without the carry.
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    3. CO@aaronman I posted this question first in computer science QA site, but someone said me to post here, Link :- http://cs.stackexchange.com/questions/18194/algorithm-to-add-sum-of-every-possible-xor-sum-sub-array
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