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Fixed merge sort, added quicksort

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1 parent 3f7b8fa commit 3d611c1617560af6840239e3d5b4593b025554d1 @nzakas committed Nov 17, 2012
@@ -55,12 +55,18 @@ function merge(left, right){
* @return {Array} The sorted array.
*/
function mergeSort(items){
- if (items.length == 1) {
+
+ // Terminal condition - don't need to do anything for arrays with 0 or 1 items
+ if (items.length < 2) {
return items;
}
- var work = [];
- for (var i=0, len=items.length; i < len; i++){
+ var work = [],
+ i,
+ len;
+
+
+ for (i=0, len=items.length; i < len; i++){
work.push([items[i]]);
}
work.push([]); //in case of odd number of items
@@ -0,0 +1,68 @@
+/*
+ * Recursive merge sort implementation in JavaScript
+ * Copyright (c) 2012 Nicholas C. Zakas
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+/**
+ * Merges to arrays in order based on their natural
+ * relationship.
+ * @param {Array} left The first array to merge.
+ * @param {Array} right The second array to merge.
+ * @return {Array} The merged array.
+ */
+function merge(left, right){
+ var result = [],
+ il = 0,
+ ir = 0;
+
+ while (il < left.length && ir < right.length){
+ if (left[il] < right[ir]){
+ result.push(left[il++]);
+ } else {
+ result.push(right[ir++]);
+ }
+ }
+
+ return result.concat(left.slice(il)).concat(right.slice(ir));
+}
+
+/**
+ * Sorts an array in ascending natural order using
+ * merge sort.
+ * @param {Array} items The array to sort.
+ * @return {Array} The sorted array.
+ */
+function mergeSort(items){
+
+ if (items.length < 2) {
+ return items;
+ }
+
+ var middle = Math.floor(items.length / 2),
+ left = items.slice(0, middle),
+ right = items.slice(middle),
+ params = merge(mergeSort(left), mergeSort(right));
+
+ // Add the arguments to replace everything between 0 and last item in the array
+ params.unshift(0, items.length);
+ items.splice.apply(items, params);
+ return items;
+}
@@ -0,0 +1,104 @@
+/*
+ * Insertion sort implementation in JavaScript
+ * Copyright (c) 2012 Nicholas C. Zakas
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of items software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and items permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+/**
+ * Swaps two values in an array.
+ * @param {Array} items The array containing the items.
+ * @param {int} firstIndex Index of first item to swap.
+ * @param {int} secondIndex Index of second item to swap.
+ * @return {void}
+ */
+function swap(items, firstIndex, secondIndex){
+ var temp = items[firstIndex];
+ items[firstIndex] = items[secondIndex];
+ items[secondIndex] = temp;
+}
+
+function partition(items, left, right) {
+
+ var pivot = items[Math.ceil((right + left) / 2)], // pivot value is middle item
+ i = left, // starts from left and goes right to pivot index
+ j = right; // starts from right and goes left to pivot index
+
+
+ // while the two indices don't match
+ while (i <= j) {
+
+ // if the item on the left is less than the pivot, continue right
+ while (items[i] < pivot) {
+ i++;
+ }
+
+ // if the item on the right is greater than the pivot, continue left
+ while (items[j] > pivot) {
+ j--;
+ }
+
+ // if the two indices still don't match, swap the values
+ if (i <= j) {
+ swap(items, i, j);
+
+ // change indices to continue loop
+ i++;
+ j--;
+ }
+ }
+
+ // this value is necessary for recursion
+ return i;
+}
+
+/**
+ * A quicksort implementation in JavaScript. The array
+ * is sorted in place.
+ * @param {Array} items An array of items to sort.
+ * @return {Array} The sorted array.
+ */
+function quickSort(items, left, right) {
+
+ var index;
+
+ // performance - don't sort an array with zero or one items
+ if (items.length > 1) {
+
+ // fix left and right values - might not be provided
+ left = typeof left != "number" ? 0 : left;
+ right = typeof right != "number" ? items.length - 1 : right;
+
+ // split up the entire array
+ index = partition(items, left, right);
+
+ // if the returned index
+ if (left < index - 1) {
+ quickSort(items, left, index - 1);
+ }
+
+ if (index < right) {
+ quickSort(items, index + 1, right);
+ }
+
+ }
+
+ return items;
+}
+

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