Most reliable and fastest way to get differences between two lists

[Mike Wilson]

I have a text file that holds a long list of number collections. I loop through the text file list capturing the rows number collection (list 1) and then have to compare that iterations number collection (list 1) against a collection of numbers from a table (list 2). The list is 300-500 rows, and the iteration collection for comparison holds 15-30 numbers. I need to determine the difference between the iteration collection (list 1) and the table collection (list 2). I know of several ways it can be done, word_subtract list 1 against list 2 and vica versa, loop through list 1 with if is_one_of(foo,list2) and vica versa and maybe others. I'd like to know others' simplest, best, favorite method for this. Thanks.

list 1 (iteration capture from text file)
1,2,4,6,8,9,11,15,16,17,22,23,24,25,26,28,30

list 2 (list from table)
1,2,4,6,7,9,10,11,15,16,17,21,23,24,25,26,30

differences
7,8,10,21,22,28

[alexc]

Re: Most reliable and fastest way to get differences between two lists

look at stack overflow

https://stackoverflow.com/questions/...google_rich_qa

Array.prototype.diff = function(a) {
    return this.filter(function(i) {return a.indexOf(i) < 0;});
};

////////////////////  
// Examples  
////////////////////

[1,2,3,4,5,6].diff( [3,4,5] );  
// => [1, 2, 6]

["test1", "test2","test3","test4","test5","test6"].diff(["test1","test2","test3","test4"]);  
// => ["test5", "test6"]

or

function arr_diff (a1, a2) {

    var a = [], diff = [];

    for (var i = 0; i < a1.length; i++) {
        a[a1[i]] = true;
    }

    for (var i = 0; i < a2.length; i++) {
        if (a[a2[i]]) {
            delete a[a2[i]];
        } else {
            a[a2[i]] = true;
        }
    }

    for (var k in a) {
        diff.push(k);
    }

    return diff;
}

console.log(arr_diff(['a', 'b'], ['a', 'b', 'c', 'd']));
console.log(arr_diff("abcd", "abcde"));
console.log(arr_diff("zxc", "zxc"));

[Stan Mathews]

Re: Most reliable and fastest way to get differences between two lists

list_1 = "1,2,4,6,8,9,11,15,16,17,22,23,24,25,26,28,30"
list_2 = "1,2,4,6,7,9,10,11,15,16,17,21,23,24,25,26,30"

same =  word_in_common(comma_to_crlf(list_1),comma_to_crlf(list_2))

ttl_list = comma_to_crlf(list_1+","+list_2)
diff_list = sortsubstr(crlf_to_comma(word_subtract(ttl_list,same)),",","A","N")
? diff_list
= "7,8,10,21,22,28"

Which can be reduced to the one line

diff_list = sortsubstr(crlf_to_comma(word_subtract(comma_to_crlf(list_1+","+list_2),word_in_common(comma_to_crlf(list_1),comma_to_crlf(list_2)))),",","A","N")
? diff_list
= "7,8,10,21,22,28"

[Mike Wilson]

Re: Most reliable and fastest way to get differences between two lists

Nice examples. Stan, I understand yours - Get what's the same and subtract from all to get what's different. Nice! An approach that I didn't think of being too wrapped up in List Processing and neglected Character Extraction functions. Thank you.

[Stan Mathews]

Re: Most reliable and fastest way to get differences between two lists

That's the best part of the message board. Throw it out there and see how someone else would solve it.

I created a function to do it but you probably did the same.

word_diff - 06-12-2018 -1.txt