Update 5.mergeSort.md

Author: shouao

5.mergeSort.md

@@ -226,16 +226,8 @@ function merge($left, $right)
 
 ## 9. C++ 代码实现
 
-### 9.1 递归版
-
 ```cpp
-void mergeSort(vector<int>& nums, int l, int r) {
-    if (r - l <= 1) {
-       return;
-    }
-    int mid = (l + r) / 2;
-    mergeSort(nums, l, mid);
-    mergeSort(nums, mid, r);
+void merge(vector<int>& nums, int l, int mid, int r) {
     int index = 0;
     int ptrL = l;
     int ptrR = mid;
@@ -251,40 +243,17 @@ void mergeSort(vector<int>& nums, int l, int r) {
         tempary[index++] = nums[ptrL++];
     }
     while (ptrR != r) {
-       tempary[index++] = nums[ptrR++];
+        tempary[index++] = nums[ptrR++];
     }
     copy(tempary.begin(), tempary.begin() + index, nums.begin() + l);
 }
-```
-
-### 9.2 迭代版
-
-```cpp
-void mergeSort(vector<int>& nums) {
-    for (int step = 1; step <= nums.size(); step *= 2) {
-        for (int i = 0; i + step < nums.size(); i += 2 * step) {
-            int l = i;
-            int r = min((int)nums.size(), i + step * 2);
-            int mid = i + step;
-            int index = 0;
-            int ptrL = l;
-            int ptrR = mid;
-            static vector<int>tempary(50000);
-            while (ptrL != mid && ptrR != r) {
-                if (nums[ptrL] < nums[ptrR]) {
-               		tempary[index++] = nums[ptrL++];
-                } else {
-                	tempary[index++] = nums[ptrR++];
-                }
-            }
-            while (ptrL != mid) {
-            	tempary[index++] = nums[ptrL++];
-            }
-            while (ptrR != r) {
-            	tempary[index++] = nums[ptrR++];
-            }
-            copy(tempary.begin(), tempary.begin() + index, nums.begin() + l);
-        }
+void mergeSort(vector<int>& nums, int l, int r) {
+    if (r - l <= 1) {
+        return;
     }
+    int mid = (l + r) / 2;
+    mergeSort(nums, l, mid);
+    mergeSort(nums, mid, r);
+    merge(nums, l, mid, r);
 }
-```
+```