init commit

3sem/cnts/contest1/05.c

@@ -0,0 +1,78 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+void
+swap(int *a, int *b)
+{
+    int temp = *a;
+    *a = *b;
+    *b = temp;
+
+    return;
+}
+
+int
+next_permutation(int *arr, int n)
+{
+    int i = n - 2;
+
+    while (i >= 0 && arr[i] >= arr[i + 1]) {
+        i--;
+    }
+
+    if (i < 0) {
+        return 0;
+    }
+
+    int j = n - 1;
+
+    while (arr[j] <= arr[i]) {
+        j--;
+    }
+
+    swap(&arr[i], &arr[j]);
+
+    int pt1 = i + 1, pt2 = n - 1;
+
+    while (pt1 < pt2) {
+        swap(&arr[pt1++], &arr[pt2--]);
+    }
+
+    return 1;
+}
+
+int
+main()
+{
+    int n;
+
+    if (scanf("%d", &n) != 1) {
+        fprintf(stderr, "Error reading input\n");
+        return 1;
+    }
+
+    if (n <= 0 || n >= 10) {
+        return 1;
+    }
+
+    int *arr = (int *) malloc(n * sizeof(*arr));
+    if (arr == NULL) {
+        return 1;
+    }
+
+    for (int i = 0; i < n; i++) {
+        arr[i] = i + 1;
+    }
+
+    do {
+        for (int i = 0; i < n; i++) {
+            printf("%d", arr[i]);
+        }
+
+        printf("\n");
+    } while (next_permutation(arr, n));
+
+    free(arr);
+
+    return 0;
+}