Export the max subarray algorithm

mgechev · mgechev · commit fc1efaeb0276 · 2014-03-12T10:08:01.000+02:00
diff --git a/src/searching/subarray/maximum-subarray-divide-and-conquer.js b/src/searching/subarray/maximum-subarray-divide-and-conquer.js
@@ -1,67 +1,75 @@
 /**
- * Finds the maximum subarray using the divide and conquer algorithm 
+ * Finds the maximum subarray using the divide and conquer algorithm
  * by Bentley, Jon (1984) (complexity O(n(logn)));
  */
 
-/**
- * Accepts an array and range. Finds the maximum sum of elements
- * around the middle of the range.
- *
- * @param {array} array
- * @param {number} left - the left interval of the range
- * @param {number} middle - the middle of the range
- * @param {number} right - the right side of the range
- * @return {number} the maximum sum including the middle element
- */
-function crossSubarray(array, left, middle, right) {
-  var leftSum = -Infinity,
-      rightSum = -Infinity,
-      sum = 0,
-      i;
+(function (exports) {
+
+  'use strict';
 
-  for (i = middle; i >= left; i -= 1) {
-    if (sum + array[i] >= leftSum) {
-      leftSum = sum + array[i];
+  /**
+   * Accepts an array and range. Finds the maximum sum of elements
+   * around the middle of the range.
+   *
+   * @param {array} array
+   * @param {number} left - the left interval of the range
+   * @param {number} middle - the middle of the range
+   * @param {number} right - the right side of the range
+   * @return {number} the maximum sum including the middle element
+   */
+  function crossSubarray(array, left, middle, right) {
+    var leftSum = -Infinity,
+        rightSum = -Infinity,
+        sum = 0,
+        i;
+
+    for (i = middle; i >= left; i -= 1) {
+      if (sum + array[i] >= leftSum) {
+        leftSum = sum + array[i];
+      }
+      sum += array[i];
+    }
+    sum = 0;
+    for (i = middle + 1; i < right; i += 1) {
+      if (sum + array[i] >= rightSum) {
+        rightSum = sum + array[i];
+      }
+      sum += array[i];
     }
-    sum += array[i];
+    return leftSum + rightSum;
   }
-  sum = 0;
-  for (i = middle + 1; i < right; i += 1) {
-    if (sum + array[i] >= rightSum) {
-      rightSum = sum + array[i];
+
+  /**
+   * Using divide and conquer finds the maximum sum of subarray of the given
+   *
+   * @param {array} array
+   * @param {number} left side of the range
+   * @param {number} the right side of the range
+   * @return {number} the maximum sum of the elements of
+   *                      subarray whithin the given range
+   */
+  function maxSubarrayPartitioner(array, left, right) {
+    if (right - left <= 1) {
+      return array[left];
     }
-    sum += array[i];
+    var middle = Math.floor((left + right) / 2),
+        leftSum = maxSubarrayPartitioner(array, left, middle),
+        rightSum = maxSubarrayPartitioner(array, middle, right),
+        crossSum = crossSubarray(array, left, middle, right);
+
+    return Math.max(crossSum, leftSum, rightSum);
   }
-  return leftSum + rightSum;
-}
 
-/**
- * Using divide and conquer finds the maximum sum of subarray of the given
- *
- * @param {array} array
- * @param {number} left side of the range
- * @param {number} the right side of the range
- * @return {number} the maximum sum of the elements of
- *                      subarray whithin the given range
- */
-function maxSubarrayPartitioner(array, left, right) {
-  if (right - left <= 1) {
-    return array[left];
+  /**
+   * Returns the maximum sum of the elements of a subarray of the given array
+   *
+   * @param {array} the array
+   * @return the maximum sum
+   */
+  function maxSubarray(array) {
+    return maxSubarrayPartitioner(array, 0, array.length);
   }
-  var middle = Math.floor((left + right) / 2),
-      leftSum = maxSubarrayPartitioner(array, left, middle),
-      rightSum = maxSubarrayPartitioner(array, middle, right),
-      crossSum = crossSubarray(array, left, middle, right);
 
-  return Math.max(crossSum, leftSum, rightSum);
-}
+  exports.maxSubarray = maxSubarray;
 
-/**
- * Returns the maximum sum of the elements of a subarray of the given array
- *
- * @param {array} the array
- * @return the maximum sum
- */
-function maxSubarray(array) {
-  return maxSubarrayPartitioner(array, 0, array.length);
-}
+}(typeof exports === 'undefined' ? window : exports));
