92 lines
2 KiB
C
92 lines
2 KiB
C
#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#define BUFFER_SIZE 256
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int count_lines(char *filename);
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int compare_ints(const void *a, const void *b);
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int main() {
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FILE *file;
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char filename[] = "input.txt";
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char *buffer = malloc(BUFFER_SIZE);
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char *saveptr;
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char *current_number_string;
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const int lines = count_lines(filename);
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int *first_numbers = malloc(lines * sizeof(int));
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int *second_numbers = malloc(lines * sizeof(int));
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int current_position = 0;
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int count = 0;
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int sum = 0;
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file = fopen(filename, "r");
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if (file == NULL) {
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perror("Error opening file");
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return 1;
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}
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while (fgets(buffer, BUFFER_SIZE, file) != NULL) {
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char *line = buffer;
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int is_first = 1;
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while ((current_number_string = strtok_r(line, " ", &saveptr))) {
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if (current_number_string[strlen(current_number_string) - 1] == '\n') {
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current_number_string[strlen(current_number_string) - 1] = '\0';
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}
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if (is_first) {
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first_numbers[current_position] = atoi(current_number_string);
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} else {
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second_numbers[current_position] = atoi(current_number_string);
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}
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is_first ^= 1;
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if (line) {
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line = NULL;
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}
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}
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current_position++;
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}
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qsort(first_numbers, lines, sizeof(int), compare_ints);
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qsort(second_numbers, lines, sizeof(int), compare_ints);
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for (int i = 0; i < lines; i++) {
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for (int j = 0; j < lines; j++) {
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if (first_numbers[i] == second_numbers[j]) {
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count++;
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} else if (count != 0) {
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sum += first_numbers[i] * count;
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count = 0;
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break;
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}
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}
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}
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printf("%d\n", sum);
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fclose(file);
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return 0;
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}
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int count_lines(char *filename) {
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char c;
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int lines = 0;
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FILE *file = fopen(filename, "r");
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if (!file) {
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return 0;
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}
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while (!feof(file)) {
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c = fgetc(file);
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if (c == '\n') {
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lines++;
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}
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}
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fclose(file);
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return lines;
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}
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int compare_ints(const void *a, const void *b) {
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return (*(int *)a - *(int *)b);
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}
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