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POWhy my insertion sort function does not change the array that I passed from int main?
 

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  1. POWhy my insertion sort function does not change the array that I passed from int main?
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    <p><strong>SHORT VERSION (Using hard-wired input)</strong></p> <pre><code>#include &lt;iostream&gt; #include &lt;string&gt; #include &lt;vector&gt; using namespace std; void insertionSort(string theArray[], int n) { //unsorted = first index of the unsorted region, //loc = index of insertion in the sorted region, //nextItem = next item in the unsorted region, //Initially, sorted region is theArray[0] // unsorted region is theArray [1..n-1]. //In general, sorted region is theArray[0..unsorted-1], // unsorted region theArray[unsorted.. n-1] for(int unsorted = 1; unsorted&lt; n; unsorted++) { //At this point, theArray[0..unsorted-1] is sorted. //Find the right position (loc) in theArray[0..unsorted] //for theArray[unsorted], which is the first entry in the //unsorted region; shift, if necessary, to make room string nextItem = theArray[unsorted]; int loc = unsorted; while( (loc &gt; 0) &amp;&amp; (theArray[loc-1] &gt; nextItem) ) { //shift theArray [loc -1] to the right theArray[loc] = theArray[loc-1]; } // At this point, theArray[loc] is where nexItem belongs theArray[loc] = nextItem; // Insert nextItem into sorted region loc--; }// end for } int main() { vector&lt;string&gt; token; int countToken; string input= "I,love,doing,nothing,at,all"; int count =0; for(int i=0; i&lt; input.length(); i++) { if(input[i] == ',') count++; } countToken = count +1; for(int i=0; i&lt; countToken; i++) { int x= input.find(','); token.push_back(input.substr(0,x)); input = input.substr(x+1); } cout &lt;&lt; endl &lt;&lt; "Current String: "; for(int i =0; i&lt; countToken; i++) { cout &lt;&lt; token[i] &lt;&lt;" " ; } cout &lt;&lt; endl; string theArray[countToken]; for(int i =0; i&lt; countToken; i++) { theArray[i] = token[i]; } insertionSort(theArray, countToken); cout &lt;&lt; "SORTED: " ; for(int i =0; i&lt; countToken; i++) { cout &lt;&lt; theArray[i] &lt;&lt; " "; } return 0; }// main </code></pre> <p><strong>FULL VERSION</strong></p> <pre><code>#include &lt;iostream&gt; #include &lt;string&gt; #include &lt;vector&gt; using namespace std; void insertionSort(string theArray[], int n) { //unsorted = first index of the unsorted region, //loc = index of insertion in the sorted region, //nextItem = next item in the unsorted region, //Initially, sorted region is theArray[0] // unsorted region is theArray [1..n-1]. //In general, sorted region is theArray[0..unsorted-1], // unsorted region theArray[unsorted.. n-1] for(int unsorted = 1; unsorted&lt; n; unsorted++) { //At this point, theArray[0..unsorted-1] is sorted. //Find the right position (loc) in theArray[0..unsorted] //for theArray[unsorted], which is the first entry in the //unsorted region; shift, if necessary, to make room string nextItem = theArray[unsorted]; int loc = unsorted; while( (loc &gt; 0) &amp;&amp; (theArray[loc-1] &gt; nextItem) ) { //shift theArray [loc -1] to the right theArray[loc] = theArray[loc-1]; } // At this point, theArray[loc] is where nexItem belongs theArray[loc] = nextItem; // Insert nextItem into sorted region loc--; }// end for } int main() { vector&lt;string&gt; token; int countToken; while(1) { int answer; cout &lt;&lt; "MENU: " &lt;&lt; endl; cout &lt;&lt; "1. Input String " &lt;&lt; endl; cout &lt;&lt; "2. Sort " &lt;&lt; endl; cout &lt;&lt; "3. Quit " &lt;&lt; endl; cout &lt;&lt; endl; cout &lt;&lt; "Response: "; cin &gt;&gt; answer; cin.ignore(1000, 10); if( answer == 1) // case 1. Input String { string input; cout &lt;&lt; endl &lt;&lt; "Default delimiter is ','"&lt;&lt; endl &lt;&lt; "Enter String: " ; getline(cin, input); // find delimiter int count =0; for(int i=0; i&lt; input.length(); i++) { if(input[i] == ',') count++; } //cout &lt;&lt; "Count: "&lt;&lt; count &lt;&lt;endl; //clear previous vector token.clear(); countToken = count +1; for(int i=0; i&lt; countToken; i++) { int x= input.find(','); token.push_back(input.substr(0,x)); input = input.substr(x+1); } //cout &lt;&lt; "countToken: " &lt;&lt; countToken &lt;&lt; endl; cout &lt;&lt; endl &lt;&lt; "Current String: "; for(int i =0; i&lt; countToken; i++) { cout &lt;&lt; token[i] &lt;&lt;" " ; } cout &lt;&lt; endl; } else if(answer == 2) // case 2. Sort { string theArray[countToken]; for(int i =0; i&lt; countToken; i++) { theArray[i] = token[i]; } //cout &lt;&lt; "COUNTTOKEN: "&lt;&lt; countToken; insertionSort(theArray, countToken); cout &lt;&lt; "SORTED: " ; for(int i =0; i&lt; countToken; i++) { cout &lt;&lt; theArray[i] &lt;&lt; " "; } } else if(answer == 3) { break; } else { cout &lt;&lt; endl &lt;&lt; "Invalid input !" &lt;&lt; endl &lt;&lt; endl; } cout &lt;&lt; endl; }// while return 0; }// main </code></pre> <p>Hi, a brief explanation of my program. I asked user to input a set of string with ',' as delimiter to cut the string off every time ',' is found, and push it to a vector, then pass it to an array, then pass the array to an insertion sort function. (nb: program will not cut correctly if there is any spaces involved in the string)</p> <p>However, my insertion sort function does not seem to change the array that I passed correctly. My program even crashes when I called the function. I read an article, and it said that <strong>arrays are by default passed by reference</strong> Thus, I do not think an ampersand '&amp;' in my function's parameter is necessary to change my array in main. </p> <p>I hope somebody can figure out what's missing in my program Any comments will be much appreciated</p> <p>Thanks</p>
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    1. USdodgerblue
    1. USdodgerblue
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      1. POWhy my insertion sort function does not change the array that I passed from int main?
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      1. VTUpMod
    1. COreduce the program to the smallest example you can
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      1. POWhy my insertion sort function does not change the array that I passed from int main?
      1. USKal
    2. CO@Kal Of course, hope it looks better
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      1. POWhy my insertion sort function does not change the array that I passed from int main?
      1. USdodgerblue
    3. COur insertion sort is wrong, try it again
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      1. POWhy my insertion sort function does not change the array that I passed from int main?
      1. USKal
 

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