Merge pull request #61 from olshansky/feat/counting-sort

feat: add counting and flash sorts

Author: ms10398

Sorts/countingSort.js

@@ -0,0 +1,37 @@
+/*
+ * Counting sort is an algorithm for sorting a collection of objects according to keys that are small integers;
+ * that is, it is an integer sorting algorithm.
+ * more information: https://en.wikipedia.org/wiki/Counting_sort
+ * counting sort visualization: https://www.cs.usfca.edu/~galles/visualization/CountingSort.html
+ */
+
+function countingSort(arr, min, max) {
+  let i;
+  let z = 0;
+  const count = [];
+  
+  for (i = min; i <= max; i++) {
+    count[i] = 0;
+  }
+  
+  for (i = 0; i < arr.length; i++) {
+    count[arr[i]]++;
+  }
+  
+  for (i = min; i <= max; i++) {
+    while (count[i]-- > 0) {
+      arr[z++] = i;
+    }
+  }
+  
+  return arr;
+}
+
+const arr = [3, 0, 2, 5, 4, 1];
+
+// Array before Sort
+console.log("-----before sorting-----");
+console.log(arr);
+// Array after sort
+console.log("-----after sorting-----");
+console.log(countingSort(arr, 0, 5));

Sorts/flashSort.js

@@ -0,0 +1,85 @@
+/*
+ * Flashsort is a distribution sorting algorithm showing linear computational complexity O(n) for uniformly distributed
+ * data sets and relatively little additional memory requirement.
+ * more information: https://en.wikipedia.org/wiki/Flashsort
+ */
+
+function flashSort(arr) {
+  let max = 0, min = arr[0];
+  let n = arr.length;
+  let m = ~~(0.45 * n);
+  let l = new Array(m);
+  
+  for (let i = 1; i < n; ++i) {
+    if (arr[i] < min) {
+      min = arr[i];
+    }
+    if (arr[i] > arr[max]) {
+      max = i;
+    }
+  }
+  
+  if (min === arr[max]) {
+    return arr;
+  }
+  
+  let c1 = (m - 1) / (arr[max] - min);
+  
+  for (let k = 0; k < m; k++) {
+    l[k] = 0;
+  }
+  
+  for (let j = 0; j < n; ++j) {
+    k = ~~(c1 * (arr[j] - min));
+    ++l[k];
+  }
+  
+  for (let p = 1; p < m; ++p) {
+    l[p] = l[p] + l[p - 1];
+  }
+  
+  let hold = arr[max];
+  arr[max] = arr[0];
+  arr[0] = hold;
+  
+  // permutation
+  let move = 0, t, flash;
+  j = 0;
+  k = m - 1;
+  
+  while (move < (n - 1)) {
+    while (j > (l[k] - 1)) {
+      ++j;
+      k = ~~(c1 * (arr[j] - min));
+    }
+    if (k < 0) break;
+    flash = arr[j];
+    while (j !== l[k]) {
+      k = ~~(c1 * (flash - min));
+      hold = arr[t = --l[k]];
+      arr[t] = flash;
+      flash = hold;
+      ++move;
+    }
+  }
+  
+  // insertion
+  for (j = 1; j < n; j++) {
+    hold = arr[j];
+    i = j - 1;
+    while (i >= 0 && arr[i] > hold) {
+      arr[i + 1] = arr[i--];
+    }
+    arr[i + 1] = hold;
+  }
+  return arr;
+}
+
+const array = [3, 0, 2, 5, -1, 4, 1, -2];
+
+// Array before Sort
+console.log("-----before sorting-----");
+console.log(array);
+// Array after sort
+console.log("-----after sorting-----");
+console.log(flashSort(array));