Split 2D array into multiple arrays using delimiter
I converted a JavaScript spritesheet to a 2D array of integers and now I am trying to split a 2D array of integers into multiple 2D arrays using 1 as the "separator" number.
Is there a way to split a 2D JavaScript array as shown below into multiple arrays using the separator number as shown below?
function separate2DArray(arrToSeparate, separator){
//separate the 2D array into multiple 2D arrays, using a
//specific number as the separator
}
//array to separate:
[
[5, 5, 5, 1, 5, 4, 5],
[5, 5, 4, 1, 4, 3, 4],
[1, 1, 1, 1, 1, 1, 1], //1 is the "separator number", which splits the array
[9, 2, 1, 4, 2, 4, 5], //horizontally and vertically
]
//The array above would produce the following 2D arrays:
5 5 5
5 5 4
5 4 5
4 3 4
9 2
4 2 4 5
The main application for this algorithm that I have in mind is splitting images into a spritesheet.
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2 answers
Given that the selected areas are rectangular, this will work:
function separate2DArray(array, sep){
//separate the 2D array into multiple 2D arrays, using a
//specific number as the separator
var result = [],
currentSubs = {}; // using x coordinate as key
for (var y=0; y<array.length; y++) {
var line = array[y],
subBegin = 0;
for (var x=0; x<=line.length; x++) {
if (x == line.length || line[x] == sep) {
if (subBegin < x) {
var sub = line.slice(subBegin, x);
if (subBegin in currentSubs)
currentSubs[subBegin].push(sub);
else
currentSubs[subBegin] = [sub];
} else { // a line of separators, subBegin == x
if (subBegin in currentSubs) {
result.push(currentSubs[subBegin]);
delete currentSubs[subBegin];
}
}
subBegin = x+1;
}
}
}
for (var begin in currentSubs)
result.push(currentSubs[begin]);
return result;
}
The result here is a very simple array of subareas without any information about their position in the original area. Improved version:
function separate2DArray(array, sep){
var result = [],
currentSubs = {};
for (var y=0; y<array.length; y++) {
var line = array[y],
subBegin = 0;
for (var x=0; x<=line.length; x++) {
if (x == line.length || line[x] == sep) {
if (subBegin < x) {
var subline = line.slice(subBegin, x);
if (! (subBegin in currentSubs)) {
var subarea = [];
result.push({x:x, y:y, area:subarea});
currentSubs[subBegin] = subarea;
}
currentSubs[subBegin].push(subline);
} else {
if (subBegin in currentSubs)
delete currentSubs[subBegin];
}
subBegin = x+1;
}
}
}
return result;
}
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You will need to iterate over the array, grabbing the preview entries into a sub array when you find 1
var arr = [[5, 5, 5, 1, 5, 4, 5], [5, 5, 4, 1, 4, 3, 4], [1, 1, 1, 1, 1, 1, 1], [9, 2, 1, 4, 2, 4, 5]];
var twoD = [];
for (var x = 0; x < arr.length; x++) {
var row = arr[x];
var subArray = [], subArrays=[];
for (var y = 0; y < row.length; y++) {
if (row[y] == 1) {
if (subArray.length) subArrays.push(subArray.slice(0));
subArray = [];
}
else {
subArray.push(row[y]);
}
}
if (subArray.length) subArrays.push(subArray);
if(subArrays.length) twoD.push(subArrays);
}
console.log(twoD);
document.write(JSON.stringify(twoD));
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