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POSmall issue in recursive array program
 

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  1. POSmall issue in recursive array program
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    <p>I'm having a bit of trouble with a recursive function. I pass an array containing integers into it, an then the function either adds or subtracts them all together. I got the addition function implemented correctly, but I am having a hard time getting the subtraction bit correct. </p> <p>Here is what I've noticed: size is currently set to 5. To test it I change the if(i == size) line in the subtraction part of the function to if(i == (size - 3)), and it appears to subtract the second element correctly from the first element (4 - 2). But if I let it run again, I get 9, instead of (4-2) - 7 = -5, which I should get. Is it adding a -7, perhaps? </p> <p>Also, I am really grateful for all pointers, but I also acknowledge that this may not be the most efficient program to accomplish what I'm trying to do. I'm a beginning programmer, and it would help me most to see where I've gone wrong in my current program, as opposed to how I should have done my algorithm instead.</p> <pre><code>#include&lt;iostream&gt; using namespace std; int reduceArray(int array[], int size, char op, int i = 0) { if(op == '+') { if(size == 0) return 0; if(i == size) return 0; else { return array[i++] + reduceArray(array, size, '-', i + 1); } } else if(op == '-') { if(size == 0) return 0; if(i == (size - 2)) //changing this to "size - n" changes how many numbers are subtracted return 0; else { return array[i++] - reduceArray(array, size, '-', i + 1); } } } int main() { int array[] = {4, 2, 7, 1, 9}; //cout &lt;&lt; reduceArray(array, 5, '+') &lt;&lt; endl; this bit works fine works fine cout &lt;&lt; reduceArray(array, 5, '-') &lt;&lt; endl; system("pause"); return 0; } </code></pre> <p><strong>EDIT:</strong> Actually--the same thing happens for the division program. For the third element of the array (the 7), it is doing the INVERSE operation--when it should subtract, it adds, when it should divide, it multiplies--can't figure out why this is happening.</p>
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