fix(Javascript): bubble sort (#647)

algorithms/JavaScript/src/sorting/bubble-sort.js

@@ -1,21 +1,52 @@
 // Bubble Sorting JavaScript Version
 
-function bubbleSort(arr) {
-  // Copy the contents of the input array and store them as a separate variable
-  const sorted = [...arr];
+// Bubble sort is a sorting algorithm in which
+// the largest element is moved or bubbled up
+// to the end of the array in every iteration
 
-  // Loop through the copied array
-  for (let i = 0; i < sorted.length; i++) {
-    // Checks if an item in the array is
-    // greater than the item next to it (index + 1)
-    if (sorted[i] > sorted[i + 1]) {
-      // If yes, swap them
-      sorted.splice(i, 2, sorted[i + 1], sorted[i]);
+function bubbleSort(arr) {
+  // a variable to hold temporary value
+  let temp;
+
+  // a boolean flag to skip iterations if
+  // the array gets sorted mid way, happens
+  // in case of large almost sorted array
+  // as shown in the second example call
+  // to bubble sort.
+  let isNoSwap;
+
+  // the outer loop starts from one end
+  // and we decrease the no. of iterations we have
+  // to make as after every iteration, the array
+  // starts getting sorted from the top end.
+  for (let i = arr.length - 1; i > 0; i--) {
+    isNoSwap = true;
+
+    // we start the inner loop from 0 to i
+    // as after ith index the elements are sorted
+    for (let j = 0; j < i; j++) {
+      if (arr[j] > arr[j + 1]) {
+        temp = arr[j];
+        arr[j] = arr[j + 1];
+        arr[j + 1] = temp;
+        isNoSwap = false;
       }
     }
-  // Finally return the sorted array
-  return sorted;
+
+    // if there hasn't been a swap
+    // in the previous iteration
+    // the array is sorted
+    // so no point going on and on
+    // skip the iterations and get out of loop.
+    if (isNoSwap) {
+      break;
+    }
+  }
+  return arr;
 }
 
 // Log to the console and have fun
 console.log(bubbleSort([23, 34, 25, 12, 54, 11]));
+
+// example of almost sorted array
+console.log(bubbleSort([8, 1, 2, 3, 4, 5, 6, 7]));