Initial data commit

Task/Sorting-algorithms-Merge-sort/C/sorting-algorithms-merge-sort-1.c

@@ -0,0 +1,38 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+void merge (int *a, int n, int m) {
+    int i, j, k;
+    int *x = malloc(n * sizeof (int));
+    for (i = 0, j = m, k = 0; k < n; k++) {
+        x[k] = j == n      ? a[i++]
+             : i == m      ? a[j++]
+             : a[j] < a[i] ? a[j++]
+             :               a[i++];
+    }
+    for (i = 0; i < n; i++) {
+        a[i] = x[i];
+    }
+    free(x);
+}
+
+void merge_sort (int *a, int n) {
+    if (n < 2)
+        return;
+    int m = n / 2;
+    merge_sort(a, m);
+    merge_sort(a + m, n - m);
+    merge(a, n, m);
+}
+
+int main () {
+    int a[] = {4, 65, 2, -31, 0, 99, 2, 83, 782, 1};
+    int n = sizeof a / sizeof a[0];
+    int i;
+    for (i = 0; i < n; i++)
+        printf("%d%s", a[i], i == n - 1 ? "\n" : " ");
+    merge_sort(a, n);
+    for (i = 0; i < n; i++)
+        printf("%d%s", a[i], i == n - 1 ? "\n" : " ");
+    return 0;
+}

Task/Sorting-algorithms-Merge-sort/C/sorting-algorithms-merge-sort-2.c

@@ -0,0 +1,59 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+/* x and y are sorted, copy nx+ny sorted values to r */
+void merge(int nx, int*x, int ny, int*y, int*r) {
+    int i= 0, j= 0, k= 0;
+    while (i<nx && j<ny) {
+        int a= x[i], b= y[j];
+        if (a<b) {
+            r[k++]= a;
+            i++;
+        } else {
+            r[k++]= b;
+            j++;
+        }
+    }
+    if (i<nx) {
+        memcpy(r+k, i+x, (nx-i)*sizeof (int));
+    } else if (j<ny) {
+        memcpy(r+k, j+y, (ny-j)*sizeof (int));
+    }
+}
+
+void mergesort(int ny, int *y) {
+    int stride= 1, mid, *r= y, *t, *x= malloc(ny*sizeof (int));
+    while (stride < ny) {
+        stride= 2*(mid= stride);
+        for (int i= 0; i<ny; i+= stride) {
+            int lim= mid;
+            if (i+stride >= ny) {
+                if (i+mid >= ny) {
+                    memcpy(i+x, i+y, (ny-i)*sizeof (int));
+                    continue;
+                }
+                lim= ny-(i+mid);
+            }
+            merge(mid, i+y, lim, i+mid+y, i+x);
+        }
+        t= x; x= y; y=t;
+    }
+    if (y!=r) {
+        memcpy(r, y, ny*sizeof(int));
+        x= y;
+    }
+    free(x);
+}
+
+int main () {
+    int a[] = {4, 65, 2, -31, 0, 99, 2, 83, 782, 1};
+    int n = sizeof a / sizeof a[0];
+    int i;
+    for (i = 0; i < n; i++)
+        printf("%d%s", a[i], i == n - 1 ? "\n" : " ");
+    mergesort(n, a);
+    for (i = 0; i < n; i++)
+        printf("%d%s", a[i], i == n - 1 ? "\n" : " ");
+    return 0;
+}