Add MergeSort

Author: EloToJaa

MergeSort.cpp

@@ -0,0 +1,44 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+class MergeSort {
+private:
+  vector<int> nums;
+  vector<int> aux;
+
+  void merge(int left, int mid, int right) {
+    for (int i = left; i <= right; i++)
+      aux[i] = nums[i];
+
+    int i = left, j = mid + 1, k = left;
+
+    while (i <= mid && j <= right) {
+      if (aux[i] <= aux[j])
+        nums[k++] = aux[i++];
+      else
+        nums[k++] = aux[j++];
+    }
+
+    while (i <= mid)
+      nums[k++] = aux[i++];
+
+    while (j <= right)
+      nums[k++] = aux[j++];
+  }
+
+public:
+  MergeSort(const vector<int> &nums) : nums(nums) { aux.resize(nums.size()); }
+
+  void mergeSort(int left, int right) {
+    if (left >= right)
+      return;
+
+    int mid = left + ((right - left) >> 1);
+
+    mergeSort(left, mid);
+    mergeSort(mid + 1, right);
+
+    merge(left, mid, right);
+  }
+};