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Optimize "uniq" to be O(n) instead of O(n^2) #2537

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Optimize "uniq" to be O(n) instead of O(n^2) #2537

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7650f69
Optimize "uniq" to be O(n) instead of O(n^2)
May 13, 2016
e462042
Structure code to pass jslint
May 13, 2016
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16 changes: 12 additions & 4 deletions underscore.js
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Original file line number Diff line number Diff line change
Expand Up @@ -535,26 +535,34 @@
// been sorted, you have the option of using a faster algorithm.
// Aliased as `unique`.
_.uniq = _.unique = function(array, isSorted, iteratee, context) {
var hasMapSupported = typeof Map !== 'undefined';
if (!_.isBoolean(isSorted)) {
context = iteratee;
iteratee = isSorted;
isSorted = false;
}
if (iteratee != null) iteratee = cb(iteratee, context);
var result = [];
var seen = [];
var seen = hasMapSupported ? new Map() : [];
for (var i = 0, length = getLength(array); i < length; i++) {
var value = array[i],
computed = iteratee ? iteratee(value, i, array) : value;
if (isSorted) {
if (!i || seen !== computed) result.push(value);
seen = computed;
} else if (iteratee) {
if (!_.contains(seen, computed)) {
seen.push(computed);
if (hasMapSupported ? !seen.has(computed) : !_.contains(seen, computed)) {
if (hasMapSupported) {
seen.set(computed);
} else {
seen.push(computed);
}
result.push(value);
}
} else if (!_.contains(result, value)) {
} else if (hasMapSupported ? !seen.has(value) : !_.contains(result, value)) {
if (hasMapSupported) {
seen.set(value);
}
result.push(value);
}
}
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