Function to return distinct values in a 2D array

Question

I have the following 2D array

var items = [['al','bv','sd'],
             ['al','cc','ab'],
             ['cv','vv','sw'],
             ['al','bv','sd']
            ];

I need a function which will return me a similar array but with distinct values. For example, in the above array, ['al','bv','sd'] happens twice.

I would like the function to return me:

var items = [['al','bv','sd'],
             ['al','cc','ab'],
             ['cv','vv','sw']
            ];

Answer 1

Quick and dirty solution, assuming the data is small.

On each iteration, convert the row to a string. Use a dictionary to store the string with a value of True, if it is not already in the map. Also, add it to your output array. If it is already in the dictionary, go to the next item.

Example:

var d = {};
var out = [];
for( var i = 0; i < items.length; i++ ) {
    var item = items[i];
    var rep = item.toString();

    if (!d[rep]) {
        d[rep] = true;
        out.push(item);
    }
}

// out has the result

Answer 2

You have to loop two (or three times):

1. Loop through all "rows", from beginning to the end

2. Loop again, through all "rows", from beginning to the end

   • If the lists are equal, ignore it
   • Otherwise,

3. Loop through all "columns":

   • If the values are not equal, jump to the parent loop.
   • After the loop, remove the element using the .splice method.

Demo: http://jsfiddle.net/EuEHc/

Code:

for (var i=0; i<items.length; i++) {
    var listI = items[i];
    loopJ: for (var j=0; j<items.length; j++) {
        var listJ = items[j];
        if (listI === listJ) continue; //Ignore itself
        for (var k=listJ.length; k>=0; k--) {
            if (listJ[k] !== listI[k]) continue loopJ;
        }
        // At this point, their values are equal.
        items.splice(j, 1);
    }
}

Answer 3

An unconventional but easier to code version

var items = [['al','bv','sd'],
             ['al','cc','ab'],
             ['cv','vv','sw'],
             ['al','bv','sd']
            ];

var temp = {};

for ( var i in items ) {
    var serialized = JSON.stringify(items[i]);
    if ( temp[serialized] ) {
        items.splice( i, 1 );
        continue;
    }
    temp[serialized] = true;
} 

Try it here! http://jsfiddle.net/y3ccJ/1/

More conventional option:

var items = [['al','bv','sd'],
             ['al','cc','ab'],
             ['cv','vv','sw'],
             ['al','bv','sd']
            ];

var results = [];

loop: for ( var i in items ) {
    compare: for ( var j in results ) {
        for ( var k in items[i] ) {
            if ( items[i][k] !== results[j][k] ) {
                break compare;
            }
        }
        continue loop;
    }
    results.push( items[i] );
}

http://jsfiddle.net/xhrd6/