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Add timsort implementation in ANSCI C #245

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4 changes: 2 additions & 2 deletions README.md
Original file line number Diff line number Diff line change
Expand Up @@ -3261,8 +3261,8 @@ In order to achieve greater coverage and encourage more people to contribute to
<tr>
<td><a href="https://en.wikipedia.org/wiki/Timsort">Timsort</a></td>
<td> <!-- C -->
<a href="./CONTRIBUTING.md">
<img align="center" height="25" src="./logos/github.svg" />
<a href="./src/c/Timsort.c">
<img align="center" height="25" src="./logos/c.svg" />
</a>
</td>
<td> <!-- C++ -->
Expand Down
128 changes: 128 additions & 0 deletions src/c/Timsort.c
Original file line number Diff line number Diff line change
@@ -0,0 +1,128 @@
#include <stdio.h>

const int THRESHOLD = 32;

int is_odd(int n) {
return n & 1;
}

int get_fmin(int a, int b) {
if (a < b) {
return a;
}
return b;
}

int get_floor(int n) {
return n / 2;
}

void print_array(int array[], int size) {
printf("[");
for (int i = 0; i < size; i++) {
printf("%d", array[i]);
if (i != size - 1) {
printf(", ");
}
}
printf("]\n");
}

int get_run_length(int size_of_array) {
int run_length = size_of_array;
int remainder = 0;

while (run_length >= THRESHOLD) {
if (is_odd(run_length)) {
remainder = 1;
}
run_length = get_floor(run_length / 2);
}
return run_length + remainder;
}

void insertion_sort(int array[], int left_index, int right_index) {
for (int i = left_index + 1; i <= right_index; i++) {
int temp = array[i];
int j = i - 1;
while (j >= left_index && array[j] > temp) {
array[j + 1] = array[j];
j--;
}
array[j + 1] = temp;
}
}

void merge_runs(int array[], int left_index, int middle_index, int right_index) {
int left_size = middle_index - left_index + 1;
int right_size = right_index - middle_index;
int left[left_size];
int right[right_size];

for (int i = 0; i < left_size; i++) {
left[i] = array[left_index + i];
}
for (int j = 0; j < right_size; j++) {
right[j] = array[middle_index + 1 + j];
}

int i = 0;
int j = 0;
int k = left_index;

while (i < left_size && j < right_size) {
if (left[i] <= right[j]) {
array[k] = left[i];
i++;
} else {
array[k] = right[j];
j++;
}
k++;
}

while (i < left_size) {
array[k] = left[i];
i++;
k++;
}

while (j < right_size) {
array[k] = right[j];
j++;
k++;
}
}

void timsort(int array[], int size) {
int run_length = get_run_length(size);

for (int i = 0; i < size; i += run_length) {
insertion_sort(array, i, get_fmin((i + run_length - 1), (size - 1)));
}

for (int size_of_run = run_length; size_of_run < size; size_of_run *= 2) {
for (int left_index = 0; left_index < size; left_index += 2 * size_of_run) {
int middle_index = left_index + size_of_run - 1;
int right_index = get_fmin((left_index + 2 * size_of_run - 1), (size - 1));
merge_runs(array, left_index, middle_index, right_index);
}
}
}

int main() {
int array[] = { 5, 2, -2147483648, 1, 4, 5323, -1, 0, 10, 9, 8, 7, 6, 2147483647, 4, 3, 2 };
int size = sizeof(array) / sizeof(array[0]);

printf("Original array:\t");
print_array(array, size);

timsort(array, size);

printf("Sorted array:\t");
print_array(array, size);
return 0;
}