first commit

sort_closet/code-sorting/MergeSort.cpp

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+#include <iostream>
+#include <vector>
+#include <algorithm>
+
+using namespace std;
+
+void merge(vector<int> &nums, int left, int mid, int right, long long &comp_count, long long &move_count)
+{
+    int n1 = mid - left + 1;
+    int n2 = right - mid;
+
+    vector<int> L(n1), R(n2);
+
+    for (int i = 0; i < n1; i++)
+    {
+        L[i] = nums[left + i];
+        move_count++;
+    }
+    for (int j = 0; j < n2; j++)
+    {
+        R[j] = nums[mid + 1 + j];
+        move_count++;
+    }
+
+    int i = 0;
+    int j = 0;
+    int k = left;
+
+    while (i < n1 && j < n2)
+    {
+        comp_count++;
+        if (L[i] <= R[j])
+        {
+            nums[k] = L[i];
+            move_count++;
+            i++;
+        }
+        else
+        {
+            nums[k] = R[j];
+            move_count++;
+            j++;
+        }
+        k++;
+    }
+
+    while (i < n1)
+    {
+        nums[k] = L[i];
+        move_count++;
+        i++;
+        k++;
+    }
+
+    while (j < n2)
+    {
+        nums[k] = R[j];
+        move_count++;
+        j++;
+        k++;
+    }
+}
+
+void mergeSortHelper(vector<int> &nums, int left, int right, long long &comp_count, long long &move_count)
+{
+    if (left < right)
+    {
+        int mid = left + (right - left) / 2;
+        mergeSortHelper(nums, left, mid, comp_count, move_count);
+        mergeSortHelper(nums, mid + 1, right, comp_count, move_count);
+        merge(nums, left, mid, right, comp_count, move_count);
+    }
+}
+
+/*
+ * function   : implement merge sort
+ * param nums : the vector to be sorted
+ * param comp_count : count of comparisons
+ * param move_count : count of moves
+ * return     : ---
+ */
+void MergeSort(vector<int> &nums, long long &comp_count, long long &move_count)
+{
+    if (nums.empty()) return;
+    mergeSortHelper(nums, 0, nums.size() - 1, comp_count, move_count);
+}