Locate the initial occurrence of a duplicated element within an array

Question

Locate the initial occurrence of a duplicated element within an array

I need to check for duplicate values in an array element. Within my array, I have multiple objects like {S:1,R:2,V:3}. My goal is to display an alert message if there are duplicate values for the "S" element in that array.

My Approach:

var arr=[{S:1,R:2,V:3},{S:2,R:2,V:3},{S:1,R:4,V:5},{S:3,R:2,V:3}, 
         {S:2,R:2,V:3},{S:3,R:4,V:5}];
function findDuplicate()
{
var sorted_arr = arr.slice().sort();
var results = [];
for (var i = 0; i < sorted_arr.length - 1; i++) {
    if (sorted_arr[i + 1].S == sorted_arr[i].S) {
        results.push(sorted_arr[i]);
         break;
    }
}

   console.log(results);
   return results;
}

if(findDuplicate().length==1)
{
alert("S -" + findDuplicate()[0].S +" is a duplicate");
}

However, the code snippet above (referencing this answer) is not yielding the desired outcome. I am expecting an alert message stating S - 1 is a duplicate.

javascript arrays angularjs typescript ecmascript-6

Answer 1

Answer №1

Modify your loop structure to achieve the task using nested loops instead of a single loop.

var arr=[{S:1,R:2,V:3},{S:2,R:2,V:3},{S:1,R:4,V:5},{S:3,R:2,V:3}, 
         {S:2,R:2,V:3},{S:3,R:4,V:5}];
function duplicateValidation()
{
    var sorted_arr = arr.slice().sort();
    var results = [];
    for (var i = 0; i < sorted_arr.length - 1; i++) {
    var S_type = sorted_arr[i].S;
    for (var j = i; j < sorted_arr.length - 1; j++){
        if (sorted_arr[j + 1].S == S_type) {
            results.push(sorted_arr[i]);
            break;
        }
    }
 }       
   return results;
}

if(duplicateValidation().length > 1)
{
console.log("S - " + duplicateValidation()[0].S +" is duplicate");
}

Answer 2

Modify your loop structure to achieve the task using nested loops instead of a single loop.

var arr=[{S:1,R:2,V:3},{S:2,R:2,V:3},{S:1,R:4,V:5},{S:3,R:2,V:3}, 
         {S:2,R:2,V:3},{S:3,R:4,V:5}];
function duplicateValidation()
{
    var sorted_arr = arr.slice().sort();
    var results = [];
    for (var i = 0; i < sorted_arr.length - 1; i++) {
    var S_type = sorted_arr[i].S;
    for (var j = i; j < sorted_arr.length - 1; j++){
        if (sorted_arr[j + 1].S == S_type) {
            results.push(sorted_arr[i]);
            break;
        }
    }
 }       
   return results;
}

if(duplicateValidation().length > 1)
{
console.log("S - " + duplicateValidation()[0].S +" is duplicate");
}

Answer 3

Answer №2

Sorting the array may seem like an unnecessary step - why not avoid the extra iteration and check for duplicates in a more efficient way? By simply iterating through the array once, you can easily identify any duplicate values without the need for sorting.

One approach is to loop through the array, checking each item's value of "S" and determining if it has already been added to a results array. If a duplicate is found, store the index of the duplicated item in a separate duplicates array. This way, you can quickly pinpoint the indexes of all duplicate items within the array.

var arr=[{S:1,R:2,V:3},{S:2,R:2,V:3},{S:1,R:4,V:5},{S:3,R:2,V:3}, 
         {S:2,R:2,V:3},{S:3,R:4,V:5}];

var results = [];
var duplicates = [];
arr.forEach(function(obj, index){
  results.indexOf(obj.S) == -1
  ? results.push(obj.S)
  : duplicates.push(index)
})

var duplicatesLength = duplicates.length;
duplicates.length > 0
 ? console.log(duplicatesLength + ' duplicates found at index (' + duplicates.join(', ')+')')
 : console.log('No duplicates found')

//outputs: 3 duplicates found at index (2, 4, 5)
// meaning that item 0 matches item 2, item 1 matches item 4, and item 3 matches item 5

Answer 4

Sorting the array may seem like an unnecessary step - why not avoid the extra iteration and check for duplicates in a more efficient way? By simply iterating through the array once, you can easily identify any duplicate values without the need for sorting.

One approach is to loop through the array, checking each item's value of "S" and determining if it has already been added to a results array. If a duplicate is found, store the index of the duplicated item in a separate duplicates array. This way, you can quickly pinpoint the indexes of all duplicate items within the array.

var arr=[{S:1,R:2,V:3},{S:2,R:2,V:3},{S:1,R:4,V:5},{S:3,R:2,V:3}, 
         {S:2,R:2,V:3},{S:3,R:4,V:5}];

var results = [];
var duplicates = [];
arr.forEach(function(obj, index){
  results.indexOf(obj.S) == -1
  ? results.push(obj.S)
  : duplicates.push(index)
})

var duplicatesLength = duplicates.length;
duplicates.length > 0
 ? console.log(duplicatesLength + ' duplicates found at index (' + duplicates.join(', ')+')')
 : console.log('No duplicates found')

//outputs: 3 duplicates found at index (2, 4, 5)
// meaning that item 0 matches item 2, item 1 matches item 4, and item 3 matches item 5

Locate the initial occurrence of a duplicated element within an array

Answer №1

Answer №2

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