Add process fork (albeit non-functioning)
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parent
563cced7ea
commit
446ac678db
183
cpair/cpair.c
183
cpair/cpair.c
@ -26,7 +26,9 @@
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* The program does the following:
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* - No output if the array has one point
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* - The points if the array has 2 points
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* - Otherwise, the array is split in 2 parts based on the mean of X and sent to 2 different paralell child processes. The parent watches for the return code of the children and terminates with an error if any of the children exit with anything other than success.
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* - Otherwise, the array is split in 2 parts based on the mean of X and sent to 2 different paralell child processes.
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* The parent watches for the return code of the children and terminates with an error if any of the children exit
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* with anything other than success.
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*
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* Algorithm description when there are more than 2 points:
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* - P1 and P2 are the closest pairs for the first and the second part respectively.
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@ -44,18 +46,24 @@
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/// Node struct for linked list
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typedef struct node {
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/**
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* points[0] - contains the X coordinate of the point
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* points[1] - contains the Y coordinate of the point
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*
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**/
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float points[2];
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struct node * next;
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} node_t;
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float get_x_mean(node_t * head);
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float get_distance(float x1, float x2, float y1, float y2);
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node_t * find_shortest_distance(node_t * list);
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int wait_for_termination(pid_t child);
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int main(void) {
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char input[__UINT8_MAX__] = ""; ///< An array to save the input to
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int point_num = 0; ///< Save the number of points
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node_t * head = NULL;
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pid_t child_a, child_b;
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head = malloc(sizeof(node_t));
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@ -74,13 +82,13 @@ int main(void) {
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current = current -> next;
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point_num++; ///< Increase the list length
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} else {
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puts("ERROR: Ill-formed line found");
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fprintf(stderr, "ERROR: Ill-formed line found\n");
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exit(EXIT_FAILURE);
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}
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}
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if(feof(stdin) == 0) {
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puts("ERROR: An error interrupted the read");
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fprintf(stderr, "ERROR: An error interrupted the read\n");
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exit(EXIT_FAILURE);
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}
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@ -95,35 +103,98 @@ int main(void) {
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float x_mean = get_x_mean(head);
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child_a = fork();
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child_b = fork();
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node_t * first_part = malloc(sizeof(node_t));
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node_t * second_part = malloc(sizeof(node_t));
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switch(child_a){
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node_t * first_part_buff = first_part;
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node_t * second_part_buff = second_part;
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/// Separate the lists based on the mean
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current = head;
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while(current != NULL) {
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if(current -> points[0] <= x_mean) {
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first_part_buff -> points[0] = current -> points[0];
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first_part_buff -> next = malloc(sizeof(node_t));
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first_part_buff = first_part_buff -> next;
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} else {
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second_part_buff -> points[0] = current -> points[0];
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second_part_buff -> next = malloc(sizeof(node_t));
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second_part_buff = second_part_buff -> next;
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}
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current = current -> next;
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}
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/**
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* Create the pipe file descriptors and inititalize the pipes
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*
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* fd[0] - input side of pipe
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* fd[1] - output side of pipe
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*
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**/
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int pipe_a[2], pipe_b[2];
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if(pipe(pipe_a) < 0 || pipe(pipe_b) < 0) {
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fprintf(stderr, "ERROR: Failed creating the pipe\n");
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exit(EXIT_FAILURE);
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}
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pid_t child_a, child_b; ///< Create variables for the child processes
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node_t * child_a_part = NULL;
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node_t * child_b_part = NULL;
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write(pipe_a[0], first_part, sizeof(node_t)); ///< Send the first part of the array to the child
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switch(child_a = fork()) {
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case -1:
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puts("ERROR: Coudn't fork child");
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fprintf(stderr ,"ERROR: Couldn't fork child\n");
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exit(EXIT_FAILURE);
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case 0:
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puts("Child");
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if(read(pipe_a[0], child_a_part, sizeof(node_t)) < 0) {
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fprintf(stderr, "ERROR: Failed reading from pipe\n");
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exit(EXIT_FAILURE);
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}
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if(write(pipe_a[1], find_shortest_distance(child_a_part), sizeof(node_t)) < 0) {
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fprintf(stderr, "ERROR: Failed writing to pipe\n");
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exit(EXIT_FAILURE);
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}
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exit(EXIT_SUCCESS);
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break;
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default:
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write(pipe_b[0], second_part, sizeof(node_t));
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switch(child_b = fork()) {
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case -1:
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fprintf(stderr, "ERROR: Couldn't fork child\n");
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exit(EXIT_FAILURE);
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case 0:
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if(read(pipe_b[0], child_b_part, sizeof(node_t)) < 0) {
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fprintf(stderr, "ERROR: Failed reading from pipe\n");
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exit(EXIT_FAILURE);
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}
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if(write(pipe_b[1], find_shortest_distance(child_b_part), sizeof(node_t)) < 0) {
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fprintf(stderr, "ERROR: Failed writing to pipe\n");
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exit(EXIT_FAILURE);
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}
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exit(EXIT_SUCCESS);
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break;
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default:
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break;
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}
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break;
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}
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switch(child_b){
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case -1:
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puts("ERROR: Coudn't fork child");
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exit(EXIT_FAILURE);
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case 0:
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puts("Child");
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break;
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default:
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break;
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}
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if(wait_for_termination(child_a) != EXIT_SUCCESS)
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exit(EXIT_FAILURE);
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int status;
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if(wait_for_termination(child_b) != EXIT_SUCCESS)
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exit(EXIT_FAILURE);
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waitpid(child_a, &status, 0);
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waitpid(child_b, &status, 0);
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/// Free the memory
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free(head);
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free(first_part);
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free(first_part_buff);
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free(second_part);
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free(second_part_buff);
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free(current);
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exit(EXIT_SUCCESS);
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}
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@ -138,14 +209,15 @@ int main(void) {
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float get_x_mean(node_t * head) {
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node_t * current = head;
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float x_sum = 0;
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int i = 0;
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while(current -> next != NULL) {
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int i = 1;
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while(current != NULL) {
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x_sum += current -> points[0];
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current = current -> next;
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i++;
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}
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return x_sum/i;
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return x_sum/(i - 2); ///< TODO: Fix the bug with the 2 more iterations
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}
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/**
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@ -160,3 +232,64 @@ float get_x_mean(node_t * head) {
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float get_distance(float x1, float x2, float y1, float y2) {
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return sqrt(pow((x2 - x1), 2) + pow((y2 - y1), 2));
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}
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/**
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* @brief Function to find the shortest distance in a list
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* @details The function gets a list of points and finds the pair
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* with the shortest distance between them.
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* @param list - the list with points
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* @return res - a list containing the coordinates of the two closest points
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*
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**/
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node_t * find_shortest_distance(node_t * list) {
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node_t * current = list;
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node_t * next = list;
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/// Setup the result list
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node_t * res = malloc(sizeof(node_t));
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res -> next = malloc(sizeof(node_t));
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int current_shortest = 0;
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int new_shortest = 0;
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while(current != NULL) {
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next = current -> next;
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if(next != NULL) {
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new_shortest = get_distance(current -> points[0], next -> points[0], current -> points[1], next -> points[1]);
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if(new_shortest < current_shortest) {
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current_shortest = new_shortest;
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/// Save the pairs
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res -> points[0] = current -> points[0];
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res -> points[1] = current -> points[1];
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res -> next -> points[0] = next -> points[0];
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res -> next -> points[1] = next -> points[1];
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}
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current = next;
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} else
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break;
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}
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return res;
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}
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/**
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* @briefs Function that waits for a child to close
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* @details The function waits for a child to close.
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* If it closes successfully, it returns the exit status only.
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* Otherwise, it prints an error message and then returns the exit status.
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* @param child - the pid of the child process
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* @return the exist status of the child process
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*
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**/
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int wait_for_termination(pid_t child) {
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int exit_stat = 0;
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if(waitpid(child, &exit_stat, 0) < 0) {
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fprintf(stderr, "ERROR: Child did not exit successfully\n");
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}
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return WEXITSTATUS(exit_stat);
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}
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