Mergesort

mergesort.c

@@ -0,0 +1,69 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+void printarr(int* arr, int begin, int end) {
+    printf("%2d - %2d: ", begin, end);
+    for(int i = begin; i < end; i++) {
+        printf("%d, ", arr[i]);
+    }
+    printf("%d\n",arr[end]);
+}
+
+void mergesort(int* data, int begin, int end) {
+    if(begin==end) return;
+    int mid = (begin+end)/2;
+
+    mergesort(data,begin,mid);
+    mergesort(data,mid+1,end);
+
+    int iter1 = begin;
+    int iter2 = mid+1;
+    int tmp;
+
+    int * const merge = malloc((end-begin+1) * sizeof(int));
+
+    int merge_i = 0;
+
+    while(iter1 <= mid && iter2 <= end) {
+        if(data[iter1] > data[iter2]) {
+            merge[merge_i] = data[iter2];
+            merge_i++;
+            iter2++;
+        } else {
+            merge[merge_i] = data[iter1];
+            merge_i++;
+            iter1++;
+        }
+    }
+
+    while(iter1 <= mid) {
+        merge[merge_i] = data[iter1];
+        merge_i++;
+        iter1++;
+    }
+
+    while(iter2 <= end) {
+        merge[merge_i] = data[iter2];
+        merge_i++;
+        iter2++;
+    }
+
+    for(int i = begin; i <= end; i++) {
+        data[i] = merge[i-begin];
+    }
+
+    free(merge);
+}
+
+int main( int argc, char *argv[] ) {
+	
+    int a[10] = {5,0,2,4,9,1,3,8,6,7};
+
+    mergesort(a, 0, 9);
+
+    for(int i = 0; i < 10; i++) {
+        printf("%d, ", a[i]);
+    }
+    printf("\n");
+	return 0;
+}