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@@ -3,6 +3,7 @@
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#include <stdio.h>
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#include <fcntl.h>
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+// Resizes array a using realloc
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unsigned int *resize_array(unsigned int *a, size_t new_size)
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{
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unsigned int *save;
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@@ -16,12 +17,14 @@ unsigned int *resize_array(unsigned int *a, size_t new_size)
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return save;
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}
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+// Swaps the values of a and b
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void swap(unsigned int *a, unsigned int *b){
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unsigned int old_a = *a;
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*a = *b;
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*b = old_a;
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}
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+// Creates a partition for use by quicksort
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int partition(unsigned int *array, int left, int right, int pivot){
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unsigned int pivot_value = array[pivot];
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swap(&array[pivot], &array[right]);
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@@ -38,6 +41,7 @@ int partition(unsigned int *array, int left, int right, int pivot){
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return storeIndex;
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}
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+// Using partition to sort `array`
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void quicksort(unsigned int *array, int left, int right){
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if (left < right){
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int pivot = right;
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@@ -50,28 +54,42 @@ void quicksort(unsigned int *array, int left, int right){
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int main()
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{
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- int temp_size = 50;
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+ const int temp_size = 50; // How many numbers to load at once?
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int size = 1;
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+
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+ // Holds all numbers we need to sort
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unsigned int *numbers = malloc(size * sizeof *numbers);
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+
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+ // Holds the numbers recently pulled from the stream
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unsigned int *temp = malloc(temp_size * sizeof *temp);
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- int ret_val;
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+
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+ int ret_val; // Holds the return value of fread so we know how many numbers were read
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/// Loop through stdin stream grabbing `temp_size` numbers each iteration
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while ((ret_val = fread(temp, sizeof *temp, temp_size, stdin))){
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// Should not happen if EOF has been reached/we have loaded all data
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if (ret_val != 0){
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+
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+ // This looks complicated, just the math required to figure the new size of `numbers`
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int new_size = size - 1 + ret_val;
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+
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+ // Actually resize array
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numbers = resize_array(numbers, new_size * sizeof *numbers);
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+ // Go from size to new_size, putting the numbers from `temp` into `numbers`
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int temp_count = 0;
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for(int i = size - 1; i < new_size; i++){
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numbers[i] = temp[temp_count++];
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}
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+
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+ // Update `size`, now that we are done with it's previous value
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size = new_size;
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}
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}
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+
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quicksort(numbers, 0, size - 1);
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+
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for (int i = 0; i < size; i++){
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printf("%u\n", numbers[i]);
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}
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