From 563cced7ea9c03e9113703ae12ee1fd8602d5737 Mon Sep 17 00:00:00 2001
From: Ivaylo Ivanov <me@ivayloivanov.eu>
Date: Wed, 12 Dec 2018 22:06:56 +0100
Subject: [PATCH] Refactor cpair and add initial forking

---
 cpair/Makefile |   2 +-
 cpair/cpair.c  | 102 ++++++++++++++++++++++++++++++++++++++++---------
 2 files changed, 84 insertions(+), 20 deletions(-)

diff --git a/cpair/Makefile b/cpair/Makefile
index 8bdf922..61c13ca 100644
--- a/cpair/Makefile
+++ b/cpair/Makefile
@@ -4,7 +4,7 @@ TARGET = cpair
 
 all: $(TARGET).c
 	$(CC) $(CFLAGS) $(TARGET).c
-	$(CC) $(TARGET).o -o $(TARGET)
+	$(CC) $(TARGET).o -o $(TARGET) -lm
 
 install:
 	cp $(TARGET) /usr/local/bin/$(TARGET)
diff --git a/cpair/cpair.c b/cpair/cpair.c
index 8921f1d..1e8457b 100644
--- a/cpair/cpair.c
+++ b/cpair/cpair.c
@@ -38,13 +38,28 @@
 #include <stdlib.h>
 #include <string.h>
 #include <math.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/wait.h>
 
-float get_x_mean(float *points[2], int arr_len);
+/// Node struct for linked list
+typedef struct node {
+    float points[2];
+    struct node * next;
+} node_t;
 
-int main () {
+float get_x_mean(node_t * head);
+float get_distance(float x1, float x2, float y1, float y2);
+
+int main(void) {
     char input[__UINT8_MAX__] = ""; ///< An array to save the input to
-    float *points[2]; ///< A pointer to a two-valued array to save the points to
     int point_num = 0; ///< Save the number of points
+    node_t * head = NULL;
+    pid_t child_a, child_b;
+
+    head = malloc(sizeof(node_t));
+
+    node_t * current = head;
 
     while(fgets(input, __INT8_MAX__, stdin) != NULL) { ///< Read line by line
         /// Split the input by whitespace as delimiter
@@ -52,10 +67,12 @@ int main () {
         char *y = strtok(NULL, " ");
 
         if(x != NULL && y != NULL) {
-            /// Convert to float and save to the array
-            points[point_num][0] = strtof(x, NULL);
-            points[point_num][1] = strtof(y, NULL);
-            point_num++; ///< Increase the array length
+            /// Convert to float and save to the list
+            current -> points[0] = strtof(x, NULL);
+            current -> points[1] = strtof(y, NULL);
+            current -> next = malloc(sizeof(node_t));
+            current = current -> next;
+            point_num++; ///< Increase the list length
         } else {
             puts("ERROR: Ill-formed line found");
             exit(EXIT_FAILURE);
@@ -71,28 +88,75 @@ int main () {
         exit(EXIT_SUCCESS);
 
     if(point_num == 2) {
-        printf("%f %f\n", points[0][0], points[0][1]);
-        printf("%f %f\n", points[1][0], points[1][1]);
+        printf("%f %f\n", head -> points[0], head -> points[1]);
+        printf("%f %f\n", head -> next -> points[0], head -> next -> points[1]);
         exit(EXIT_SUCCESS);
     }
 
-    float x_mean = get_x_mean(points, point_num);
+    float x_mean = get_x_mean(head);
+
+    child_a = fork();
+    child_b = fork();
+
+    switch(child_a){
+        case -1:
+            puts("ERROR: Coudn't fork child");
+            exit(EXIT_FAILURE);
+        case 0:
+            puts("Child");
+            break;
+        default:
+            break;
+    }
+
+    switch(child_b){
+        case -1:
+            puts("ERROR: Coudn't fork child");
+            exit(EXIT_FAILURE);
+        case 0:
+            puts("Child");
+            break;
+        default:
+            break;
+    }
+
+    int status;
+
+    waitpid(child_a, &status, 0);
+    waitpid(child_b, &status, 0);
 
     exit(EXIT_SUCCESS);
 }
 
 /**
- * @brief Function to calculate the mean of the X coordinates from a points array
- * @details Loops through the points array, gets the sum of X coordinates and returns the mean
- * @param points - a pointer to an array with the points
- *        point_num - number of points in the array
+ * @brief Function to calculate the mean of the X coordinates from a points list
+ * @details Loops through the points list, gets the sum of X coordinates and returns the mean
+ * @param head - a pointer to a list with the points
  * @return mean of all X coordinates
  *
  **/
-float get_x_mean(float *points[2], int point_num) {
+float get_x_mean(node_t * head) {
+    node_t * current = head;
     float x_sum = 0;
-    for(int i = 0; i< point_num; i++) {
-        x_sum += points[i][0];
+    int i = 0;
+    while(current -> next != NULL) {
+        x_sum += current -> points[0];
+        current = current -> next;
+        i++;
     }
-    return x_sum/point_num;
-}
\ No newline at end of file
+
+    return x_sum/i;
+}
+
+/**
+ * @brief Function to calculate the distance between 2 points
+ * @details The function calculates the distance between 2 points
+ *          in a Cartesian coordinate system, given their coordinates
+ * @param x1, y1 - pair of coordinates for the first point
+ *        x2, y2 - pair of coordinates for the second point
+ * @return distance between the two points
+ *
+ **/
+float get_distance(float x1, float x2, float y1, float y2) {
+    return sqrt(pow((x2 - x1), 2) + pow((y2 - y1), 2));
+}