/** * @file * @brief Implementation of [merge * sort](https://en.wikipedia.org/wiki/Merge_sort) algorithm */ #include #include /** * @addtogroup sorting Sorting algorithms * @{ */ /** Swap two integer variables * @param [in,out] a pointer to first variable * @param [in,out] b pointer to second variable */ void swap(int *a, int *b) { int t; t = *a; *a = *b; *b = t; } /** * @brief Perform merge of segments. * * @param a array to sort * @param l left index for merge * @param r right index for merge * @param n total number of elements in the array */ void merge(int *a, int l, int r, int n) { int *b = (int *)malloc(n * sizeof(int)); /* dynamic memory must be freed */ int c = l; int p1, p2; p1 = l; p2 = ((l + r) / 2) + 1; while ((p1 < ((l + r) / 2) + 1) && (p2 < r + 1)) { if (a[p1] <= a[p2]) { b[c++] = a[p1]; p1++; } else { b[c++] = a[p2]; p2++; } } if (p2 == r + 1) { while ((p1 < ((l + r) / 2) + 1)) { b[c++] = a[p1]; p1++; } } else { while ((p2 < r + 1)) { b[c++] = a[p2]; p2++; } } for (c = l; c < r + 1; c++) a[c] = b[c]; free(b); } /** Merge sort algorithm implementation * @param a array to sort * @param n number of elements in the array * @param l index to sort from * @param r index to sort till */ void merge_sort(int *a, int n, int l, int r) { if (r - l == 1) { if (a[l] > a[r]) swap(&a[l], &a[r]); } else if (l != r) { merge_sort(a, n, l, (l + r) / 2); merge_sort(a, n, ((l + r) / 2) + 1, r); merge(a, l, r, n); } /* no change if l == r */ } /** @} */ /** Main function */ int main(void) { int *a, n, i; scanf("%d", &n); a = (int *)malloc(n * sizeof(int)); for (i = 0; i < n; i++) { scanf("%d", &a[i]); } merge_sort(a, n, 0, n - 1); for (i = 0; i < n; i++) { printf(" %d", a[i]); } free(a); return 0; }