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POSorting gives inconsistent results, due to loop bound
 

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  1. POSorting gives inconsistent results, due to loop bound
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    <p>Program Design, our first homework assignment was to take 4 integer values, add the 2 highest together and subtract the lowest two and square that result. Finally, compare the 2 values together to see if they are equal or not. </p> <p>For example, if you were to enter: <code>20 10 60 40</code> </p> <p>You'd get </p> <pre><code>60 + 40 = 100 </code></pre> <p>and </p> <pre><code>20 - 10 = 10 --&gt; 10^2 = 100 </code></pre> <p>So, <code>100 == 100</code></p> <p>I wrote my program and tested it for various values which all returned correct results. My professor told me my program failed for all 10 test inputs and he sent me the results he got. The results he got aren't the same as mine, and I don't know what's going on. I emailed him, and he told me one of my for loops has incorrect bounds. He's right, but I still get the right results, so...?</p> <p>Here's the code, any help would be appreciated!</p> <pre><code>/* // Author: Jesse W // Assignment 1 // Desciption: // This program inputs four integer numbers a, b, c and d and // determines if the sum of the two largest numbers is the same // as the squared difference of the two smallest numbers */ #include &lt;stdio.h&gt; /* Complete the code for this program below */ int main() { int a, b, c, d, f, k, swap; int array_size = 4; int return_val; int sum, difference, square; int small_1, small_2, large_1, large_2; int array[array_size]; //Gather input //printf("Enter integer values for a, b, c and d.\n"); return_val = scanf("%d %d %d %d", &amp;a, &amp;b, &amp;c, &amp;d); //Validate input if (return_val != 4) { printf("INVALID INPUT\n"); } else { //Assign values to array array[0] = a; array[1] = b; array[2] = c; array[3] = d; //Sort array for (k = 0 ; k &lt; ( array_size - 1 ); k++) { for (f = 0 ; f &lt; array_size ; f++) { if (array[f] &gt; array[f+1]) /* For decreasing order use &lt; */ { swap = array[f]; array[f] = array[f+1]; array[f+1] = swap; } } } //Assign sorted values to new variables small_1 = array[0]; small_2 = array[1]; large_1 = array[2]; large_2 = array[3]; //Compute math sum = large_1 + large_2; difference = small_1 - small_2; square = difference * difference; //Compute logic if(sum == square) { printf("%d equals %d.\n", sum, square); } else { printf("%d does not equal %d.\n", sum, square); } return 0; } } </code></pre>
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    1. USPotatoswatter
    1. USJesse Walton
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    1. CO`http://ideone.com/Q29DX2` I used `100 20 40 80` so your answer should be `100 + 80 = 180` and `20 - 40 = -20`, and square is `400`....but your output says `120 does not equal 361.`...so your professor is correct :) Happy debugging...
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      1. USBill
    2. CODespite the fact you shouldn't write code like that, you have an off-by-one error within your loop as you access array[array_size] which would be uninitialized value, that is either 0 or some random garbage. This can screw up things quite a bit. I'd recommend using a debugger in cases you encounter such "anomalies".
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      1. USPowerslave
    3. COWelcome to the wonderful world of debugging, where you can get the right answer and never know that your code is wrong. As everyone has already pointed out, you're accessing the array beyond its bounds. Also, your sort uses 12 compare-and-swaps when it only needs 5, but let's get it right before you worry about that. :-)
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      1. USLee Daniel Crocker
 

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