Add initial cpair functionality

.gitignore

@@ -6,3 +6,5 @@
 !public/*.html
 http/client
 http/server
+mygrep/mygrep
+cpair/cpair

README.md

@@ -3,5 +3,6 @@ This project contains some basic UNIX command line tools I had to do for TU.
 Currently the toolset is ther following:
 * mygrep - a simplified version of grep
 * http - an implementation of HTTP 1.1 client and server
+* cpair - a program that searches for the closest pair of points in a set of 2D-points
 
 Feel free to read the descriptions for each tool.

cpair/Makefile

@@ -0,0 +1,18 @@
+CC = gcc
+CFLAGS = -std=c99 -pedantic -Wall -D_DEFAULT_SOURCE -D_BSD_SOURCE -D_SVID_SOURCE -D_POSIX_C_SOURCE=200809L -g -c
+TARGET = cpair
+
+all: $(TARGET).c
+	$(CC) $(CFLAGS) $(TARGET).c
+	$(CC) $(TARGET).o -o $(TARGET)
+
+install:
+	cp $(TARGET) /usr/local/bin/$(TARGET)
+
+clean:
+	$(RM) $(TARGET).o
+	$(RM) $(TARGET)
+	$(RM) *.tgz
+
+package:
+	tar -cvzf mygrep.tgz $(TARGET).c Makefile

cpair/README.md

@@ -0,0 +1,32 @@
+# cpair
+
+A program that searches for the closest pair of points in a set of 2D-points
+
+    SYNOPSIS
+    cpair
+
+    EXAMPLE
+    $ cat 1.txt
+    4.0 4.0
+    -1.0 1.0
+    1.0 -1.0
+    -4.0 -4.0
+    $ ./cpair < 1.txt
+    -1.000000 1.000000
+    1.000000 -1.000000
+
+
+The program accepts an array of 2D-points as an input from `stdin`. The input ends at `EOF`.
+
+The program does the following:
+* No output if the array has one point
+* The points if the array has 2 points
+* 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.
+
+Algorithm description when there are more than 2 points:
+* P1 and P2 are the closest pairs for the first and the second part respectively.
+* Go through all of the pairs between the points from the first half with the second half and save the shortest one in P3.
+* Compare P1, P2 and P3 and return the shortest one to `stdout`.
+
+
+**Note: The description and the example are from the task I got from TU.**

cpair/cpair.c

@@ -0,0 +1,98 @@
+/**
+ * @file cpair.c
+ * @author Ivaylo Ivanov 11777707
+ * @date 08.12.2018
+ *
+ * @brief Main program module.
+ *
+ * A program that searches for the closest pair of points in a set of 2D-points
+ *
+ *    SYNOPSIS
+ *    cpair
+ *
+ *    EXAMPLE
+ *    $ cat 1.txt
+ *    4.0 4.0
+ *    -1.0 1.0
+ *    1.0 -1.0
+ *    -4.0 -4.0
+ *    $ ./cpair < 1.txt
+ *    -1.000000 1.000000
+ *    1.000000 -1.000000
+ *
+ *
+ * The program accepts an array of 2D-points as an input from stdin. The input ends at EOF.
+ *
+ * The program does the following:
+ *  - No output if the array has one point
+ *  - The points if the array has 2 points
+ *  - 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.
+ *
+ * Algorithm description when there are more than 2 points:
+ *  - P1 and P2 are the closest pairs for the first and the second part respectively.
+ *  - Go through all of the pairs between the points from the first half with the second half and save the shortest one in P3.
+ *  - Compare P1, P2 and P3 and return the shortest one to stdout.
+ *
+ **/
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <math.h>
+
+float get_x_mean(float *points[2], int arr_len);
+
+int main () {
+    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
+
+    while(fgets(input, __INT8_MAX__, stdin) != NULL) { ///< Read line by line
+        /// Split the input by whitespace as delimiter
+        char *x = strtok(input, " ");
+        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
+        } else {
+            puts("ERROR: Ill-formed line found");
+            exit(EXIT_FAILURE);
+        }
+    }
+
+    if(feof(stdin) == 0) {
+        puts("ERROR: An error interrupted the read");
+        exit(EXIT_FAILURE);
+    }
+
+    if(point_num == 1)
+        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]);
+        exit(EXIT_SUCCESS);
+    }
+
+    float x_mean = get_x_mean(points, point_num);
+
+    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
+ * @return mean of all X coordinates
+ *
+ **/
+float get_x_mean(float *points[2], int point_num) {
+    float x_sum = 0;
+    for(int i = 0; i< point_num; i++) {
+        x_sum += points[i][0];
+    }
+    return x_sum/point_num;
+}