Sorting an array using another array of indices
I am iterating over arrays of arrays and I need to sort them in the order of the other.
Let's say I have two arrays:
aLinks = [4,5,6]
bLinks = [1,2,3,4,5,6]
I need to return:
aLinks = [4,5,6]
bLinks = [4,5,6,1,2,3]
means I need to have the elements that match the first array at the beginning, and not the rest, sorted by order, if possible.
I am working with d3, so I use forEach to traverse linksets and keep the order of aLinks.
I don't know how to apply this order to bLinks
var linkOrder = [];
linkSets.forEach(function(set, i) {
linkOrder = [];
set.aLinks.forEach(function(link,i){
linkOrder.push(link.path);
})
});
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You can do it like:
- Take out the matched elements from the second array into a temp array
- Sorting temp array
- Sorting a second array containing only those elements that don't match
- Concatenating second array into temp array
Code - with the help of a fix provided by the user: basilikum
var first = [4,5,6];
var second = [1,7,3,4,6,5,6];
var temp = [], i = 0, p = -1;
// numerical comparator
function compare(a, b) { return a - b; }
// take out matching items from second array into a temp array
for(i=0; i<first.length; i++) {
while ((p = second.indexOf(first[i])) !== -1) {
temp.push(first[i]);
second.splice(p, 1);
}
}
// sort both arrays
temp.sort(compare);
second.sort(compare);
// concat
temp = temp.concat(second);
console.log(temp);
Working demo : http://jsfiddle.net/kHhFQ/
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A + sort(A-B)
What you end up with is - so you just need to calculate the difference between the two arrays. Using some underscore methods like:
var A = [4,5,6];
var B = [1,2,3,4,5,6];
var diff = _.difference(A,B);
var result = _.flattern(A, diff.sort());
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repeat the first array, removing the values from the second array, and then adding them to the beginning of the array to get the correct order:
var arr1 = [4,5,6];
var arr2 = [1,2,3,4,6,5];
arr1.sort(function(a,b) {return a-b;});
for (i=arr1.length; i--;) {
arr2.splice(arr2.indexOf(arr1[i]), 1);
arr2.unshift( arr1[i] );
}
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