66 lines
1.1 KiB
C
66 lines
1.1 KiB
C
#include <stdio.h>
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#include <stdlib.h>
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#define ARR_SIZE 4
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int ifactorial(int n) {
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if (n == 0) {
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return 1;
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}
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int result = 1;
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for (int i = 1; i <= n; i++) {
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result *= i;
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}
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return result;
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}
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void swap(char *a, char *b) {
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char tmp = *a;
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*a = *b;
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*b = tmp;
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}
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void permutations(char *arr, int arr_size) {
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int factorial = ifactorial(arr_size);
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int k = factorial;
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while (k > 0) {
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printf("%s\n", arr);
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int i = 1;
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while (arr[i] > arr[i - 1]) {
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i++;
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}
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int j = 0;
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while (arr[j] < arr[i]) {
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j++;
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}
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swap(&arr[j], &arr[i]);
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i--;
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for (j = 0; j < i; i--, j++) {
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swap(&arr[i], &arr[j]);
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}
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k--;
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}
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}
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int compare(const void *a, const void *b) {
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return (int)(*(char *)b - *(char *)a); // descending order
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}
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int main(void) {
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char arr[ARR_SIZE + 1] = "2431";
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qsort(arr, ARR_SIZE, sizeof(char), compare); // "4321"
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permutations(arr, ARR_SIZE);
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return EXIT_SUCCESS;
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}
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