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selection sort?

thefortrees

By thefortrees
in PHP Coding Help

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thefortrees Member

thefortrees

Posted
Posted

Hi all -

 

I need to implement some sorting algorithm.

 

I have a webpage that has n number of questions. The user can reorder the questions as desired with drop down menus.

 

Description of problem:

The questions are in position as follows: q1->1,

                                                      q2->2,

                                                      q3->3,

                                                      q4->4,

                                                      q5->5

 

If I change the position with the drop down menus, I could possibly have:

q1->1,

q2->5,

q3->3,

q4->4,

q5->5

 

Which, upon form submission would have to be reordered before being stored in the database to this:

q5->1,

q1->2,

q3->3,

q4->4,

q2->5

 

Any suggestions on where/how to start?

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https://forums.phpfreaks.com/topic/63233-selection-sort/
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Psycho Prolific Member

Psycho

Posted
Posted

I have typically used Javascript to do the renumbering before submitting for processing, but ideally you should also validate on the srver side. Your example is pretty simplistic. But, without some validation on the client-side, you are going to have some issues to deal with. What if the user was to set all the questions to #5, what then? Or if you moved item two to positin 3 and item three to position 4. Would you move item four to position 2?

 

The easiest approach in my opinion would be to simply order the options by the new sort and then do a secondary sort by the original order in reverse order.

 

Here is something I started working on this week that may help (only works on IE at the moment). But it may be a better way of allowing the user to reorder the questions:

<html>

<head>

<script type="text/javascript">


//====================================================
 function addOption (fieldObj, valueStr, textStr, index, selected) {
//====================================================
   var index = (index!==false)?index:fieldObj.length;
   var textStr = (textStr!==false)?textStr:valueStr;
   var selected = (selected==true)?true:false;

   var newOption = document.createElement('option');
   newOption.text = textStr;
   newOption.value = valueStr;
   newOption.selected = selected;

   fieldObj.add(newOption, index);
 }

//====================================================
 function deleteOption (fieldObj, optIndex) {
//====================================================
   if(fieldObj.options[optIndex]) {
     fieldObj.options[optIndex] = null;
   }
 }


//====================================================
 function orderOptions(fieldID, action) {
//====================================================
   var fieldObj = document.getElementById(fieldID);

   if (action=='down' || action=='bottom') {
     var startIdx = fieldObj.length-1;
     var endIdx = -1;
     var step = -1;
     if (action=='bottom') {
       var newIdx = fieldObj.length-1;
     } else { //action = 'down'
       for (var i=startIdx; i>=fieldObj.selectedIndex; i--) {
         if (fieldObj.options[i].selected) { var newIdx=i+1; break;}
       }
       newIdx = (newIdx>fieldObj.length-1)?fieldObj.length-1:newIdx;
     }
   } else { //action = 'up' or 'top'
     var startIdx = 0;
     var endIdx = fieldObj.length;
     var step = 1;
     if (action=='top') {
       var newIdx = 0;
     } else { // Action='up' : default
       var newIdx = (fieldObj.selectedIndex-1);
       newIdx = (newIdx<0)?0:newIdx;
     }
   }

   for (var optIdx=startIdx; optIdx!=endIdx; optIdx+=step) {

     if (fieldObj.options[optIdx].selected) {
       //Save current values
       var optSaveText = fieldObj.options[optIdx].text;
       var optSaveValue = fieldObj.options[optIdx].value;

       //Delete and recreate the option at new index
       deleteOption (fieldObj, optIdx);
       addOption (fieldObj, optSaveValue, optSaveText, newIdx, true);

       //Adjust index value
       newIdx += step;

     } //End if

   } //End for loop
   return;
 }

//====================================================
 function sortOptions(fieldID, direction) {
//====================================================
   var fieldObj = document.getElementById(fieldID);

   //Create an array of the option properties
   optionAry = new Array();
   for (var optIdx=0; optIdx<fieldObj.options.length; optIdx++) {
     op = fieldObj.options[optIdx];
     optionAry[optIdx] = new Array();
     optionAry[optIdx]['text'] = op.text;
     optionAry[optIdx]['value'] = op.value;
     optionAry[optIdx]['selected'] = op.selected;
   }

   //Sort the array
   optionAry.sort(sortOptionArray);
   if (direction=='desc') { optionAry.reverse(); }

   //Repopulate the option list
   for (var optIdx=0; optIdx<fieldObj.options.length; optIdx++) {
     fieldObj.options[optIdx].text = optionAry[optIdx]['text'];
     fieldObj.options[optIdx].value = optionAry[optIdx]['value'];
     fieldObj.options[optIdx].selected = optionAry[optIdx]['selected'];
   }
   return;
 }
 //====================================================
 function sortOptionArray (a, b) {
   var aText = a['text'].toLowerCase();
   var bText = b['text'].toLowerCase();
   if (aText < bText) { return -1; }
   if (aText > bText) { return  1; }
   return 0;
 }

 function populateFields() {
//
 }

 </script>

</head>

<body>

   <span style="border:0px solid red;width:220px;text-align:left;vertical-align:middle;">
     Assigned:<br>
     <select name="assigned" id="assigned" size="10" style="width:220px;" multiple onChange="">
     <option value="Question 1">Question 1</option>
     <option value="Question 2">Question 2</option>
     <option value="Question 3">Question 3</option>
     <option value="Question 4">Question 4</option>
     <option value="Question 5">Question 5</option>
     </select>
   </span>

   <span style="border:0px solid red;width:70px;text-align:middle;vertical-align:middle;"><br>
     <button id="moveTop"  style="width:50px;font-size:8pt;" onclick="orderOptions('assigned', 'top');"   title="Move to top">Top</button><br>
     <button id="moveUp"   style="width:50px;font-size:8pt;" onclick="orderOptions('assigned', 'up');"    title="Move up">Up</button><br>
     <button id="moveDown" style="width:50px;font-size:8pt;" onclick="orderOptions('assigned', 'down');"  title="Move down">Down</button><br>
     <button id="moveBottom" style="width:50px;font-size:8pt;" onclick="orderOptions('assigned', 'bottom');"  title="Move to bottom">Bottom</button><br>
     <br>
     <button id="sortDesc" style="width:50px;font-size:8pt;" onclick="sortOptions('assigned', 'asc');" title="Sort ascending">A-Z</button><br>
     <button id="sortAsc"  style="width:50px;font-size:8pt;" onclick="sortOptions('assigned', 'desc');" title="Sort descending">Z-A</button>
   </span>


</body>

</htmL>

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