Added merge sort algorithm to the 'c' folder in Algorithm

Algorithms/C/Merge_sort.c

@@ -0,0 +1,81 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+// 合并两个有序子数组 arr[l..m] 和 arr[m+1..r]
+void merge(int arr[], int l, int m, int r) {
+    int i, j, k;
+    int n1 = m - l + 1;
+    int n2 = r - m;
+
+    // 创建临时数组
+    int *L = (int*)malloc(n1 * sizeof(int));
+    int *R = (int*)malloc(n2 * sizeof(int));
+
+    // 拷贝数据到临时数组
+    for (i = 0; i < n1; i++)
+        L[i] = arr[l + i];
+    for (j = 0; j < n2; j++)
+        R[j] = arr[m + 1 + j];
+
+    // 合并临时数组回 arr[l..r]
+    i = 0;
+    j = 0;
+    k = l;
+    while (i < n1 && j < n2) {
+        if (L[i] <= R[j]) {
+            arr[k] = L[i];
+            i++;
+        } else {
+            arr[k] = R[j];
+            j++;
+        }
+        k++;
+    }
+
+    // 拷贝剩余元素
+    while (i < n1) {
+        arr[k] = L[i];
+        i++;
+        k++;
+    }
+    while (j < n2) {
+        arr[k] = R[j];
+        j++;
+        k++;
+    }
+
+    free(L);
+    free(R);
+}
+
+// 归并排序递归函数
+void mergeSort(int arr[], int l, int r) {
+    if (l < r) {
+        int m = l + (r - l) / 2; // 防止溢出
+        mergeSort(arr, l, m);
+        mergeSort(arr, m + 1, r);
+        merge(arr, l, m, r);
+    }
+}
+
+// 打印数组
+void printArray(int arr[], int size) {
+    for (int i = 0; i < size; i++)
+        printf("%d ", arr[i]);
+    printf("\n");
+}
+
+// 测试示例
+int main() {
+    int arr[] = {12, 11, 13, 5, 6, 7};
+    int arr_size = sizeof(arr) / sizeof(arr[0]);
+
+    printf("原始数组: ");
+    printArray(arr, arr_size);
+
+    mergeSort(arr, 0, arr_size - 1);
+
+    printf("排序后数组: ");
+    printArray(arr, arr_size);
+    return 0;
+}