98 lines
3.0 KiB
C
98 lines
3.0 KiB
C
/**
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* @file cpair.c
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* @author Ivaylo Ivanov 11777707
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* @date 08.12.2018
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*
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* @brief Main program module.
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*
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* A program that searches for the closest pair of points in a set of 2D-points
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*
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* SYNOPSIS
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* cpair
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*
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* EXAMPLE
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* $ cat 1.txt
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* 4.0 4.0
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* -1.0 1.0
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* 1.0 -1.0
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* -4.0 -4.0
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* $ ./cpair < 1.txt
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* -1.000000 1.000000
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* 1.000000 -1.000000
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*
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*
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* The program accepts an array of 2D-points as an input from stdin. The input ends at EOF.
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*
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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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*
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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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* - Go through all of the pairs between the points from the first half with the second half and save the shortest one in P3.
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* - Compare P1, P2 and P3 and return the shortest one to stdout.
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*
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**/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <math.h>
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float get_x_mean(float *points[2], int arr_len);
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int main () {
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char input[__UINT8_MAX__] = ""; ///< An array to save the input to
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float *points[2]; ///< A pointer to a two-valued array to save the points to
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int point_num = 0; ///< Save the number of points
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while(fgets(input, __INT8_MAX__, stdin) != NULL) { ///< Read line by line
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/// Split the input by whitespace as delimiter
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char *x = strtok(input, " ");
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char *y = strtok(NULL, " ");
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if(x != NULL && y != NULL) {
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/// Convert to float and save to the array
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points[point_num][0] = strtof(x, NULL);
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points[point_num][1] = strtof(y, NULL);
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point_num++; ///< Increase the array length
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} else {
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puts("ERROR: Ill-formed line found");
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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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exit(EXIT_FAILURE);
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}
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if(point_num == 1)
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exit(EXIT_SUCCESS);
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if(point_num == 2) {
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printf("%f %f\n", points[0][0], points[0][1]);
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printf("%f %f\n", points[1][0], points[1][1]);
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exit(EXIT_SUCCESS);
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}
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float x_mean = get_x_mean(points, point_num);
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exit(EXIT_SUCCESS);
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}
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/**
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* @brief Function to calculate the mean of the X coordinates from a points array
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* @details Loops through the points array, gets the sum of X coordinates and returns the mean
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* @param points - a pointer to an array with the points
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* point_num - number of points in the array
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* @return mean of all X coordinates
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*
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**/
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float get_x_mean(float *points[2], int point_num) {
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float x_sum = 0;
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for(int i = 0; i< point_num; i++) {
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x_sum += points[i][0];
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}
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return x_sum/point_num;
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} |