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POcalculate the sum of diagonals in a matrix
 

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  1. POcalculate the sum of diagonals in a matrix
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    <p>I need to calculate the sum of two diagonals in a matrix in C++, I already have a solution for that but I must be dumb because I cant understand what it is doing, so I would like to know if there is another version which I can understand. here is the code which does the job:</p> <pre><code>cout&lt;&lt;"Jepi rangun e matrices"&lt;&lt;endl; // pra bejme manipulim me matrice katrore ku rreshtat=kolonat cin&gt;&gt;n; cout&lt;&lt;"Tani jepi elementet e matrices"&lt;&lt;endl; // lexohet matrica for(i=1;i&lt;=n;i++) { for(j=1;j&lt;=n;j++) cin&gt;&gt;a[i][j]; } d=0; s=0; // ketu e keni kushtin si dhe mbledhjen per te dy diagonalet me dy variabla te ndryshme for(i=1;i&lt;=n;i++) for(j=1;j&lt;=n;j++) { if(i==j) d=d+a[i][j]; if(j==n-i+1 || i==n-j+1) s=s+a[i][j]; } </code></pre> <p>The part that is difficult to understand is</p> <pre><code>if(j==n-i+1 || i==n-j+1) s=s+a[i][j]; </code></pre> <p>Here is the entire code that I changed but it doesnt work for the secondary diagonal:</p> <pre><code>#include &lt;iostream&gt; using namespace std; int main() { int d=0,s=0; // ketu e keni kushtin si dhe mbledhjen per te dy diagonalet me dy variabla te ndryshme int i,j,n; int a[5][5]; cout&lt;&lt;"Jepi rangun e matrices"&lt;&lt;endl; // pra bejme manipulim me matrice katrore ku rreshtat=kolonat cin&gt;&gt;n; cout&lt;&lt;"Tani jepi elementet e matrices"&lt;&lt;endl; // lexohet matrica for(i=1;i&lt;=n;i++) { for(j=1;j&lt;=n;j++) cin&gt;&gt;a[i][j]; } for(i=1;i&lt;=n;i++) { for(j=1;j&lt;=n;j++) { if(i==j) d+=a[i][j]; //principal diagonal if(i+j==n-1) s+=a[i][j];//secondary diagonal } } cout &lt;&lt; d &lt;&lt; endl; cout &lt;&lt; s &lt;&lt; endl; cin.get(); cin.get(); return 0; } </code></pre>
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    1. CODo you have a specific question about any part this code?
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      1. USDrew Dormann
    2. CO@DrewDormann yeah this is the problem: if(j==n-i+1 || i==n-j+1) s=s+a[i][j];
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