93 lines
1.9 KiB
C
93 lines
1.9 KiB
C
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#include <stdlib.h>
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#include <stdio.h>
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#include <string.h>
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#include <stdbool.h>
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#define LINES 1000
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struct instruction {
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char *coord;
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struct instruction *next;
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};
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void addInstruction(struct instruction *start, char *coord)
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{
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// traverse list until last member
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while(start->next) start = start->next;
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// allocate and store ptr
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start->next = malloc(sizeof(struct instruction));
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// store coords in new item
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start->next->coord = coord;
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start->next->next = 0;
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}
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bool confirm_numbers(char *start, char *end) {
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for (int i = 0; (start[i] >= '0' && start[i] <= '9') || start[i] == ','; i++) {
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if (start[i + 1 ] == ')')
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return 1;
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}
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return 0;
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}
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int parse_numbers(char *string)
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{
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int i = 0;
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int a = 0;
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int b = 0;
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while (string[i] >= '0' && string[i] <= '9') {
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a = a * 10 + string[i] - '0';
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i++;
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}
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// skip comma!
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i++;
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while (string[i] >= '0' && string[i] <= '9') {
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b = b * 10 + string[i] - '0';
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i++;
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}
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return a * b;
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}
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int main()
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{
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unsigned int sum = 0;
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char instructions[32];
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FILE *input;
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input = fopen("./input", "r");
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fseek(input, 0L, SEEK_END);
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unsigned int fLen = ftell(input);
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char *memory = malloc(fLen * sizeof(char) + 1);
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rewind(input);
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fread(memory, fLen, sizeof(char), input);
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memory[fLen + 1] = '\0';
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fclose(input);
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// find first instruction start for the list head
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char *start = memory;
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start = strstr(start, "mul(") + 4;
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struct instruction *list = malloc(sizeof(struct instruction));
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list->coord = start;
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list->next = 0;
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// find the rest of the instructions and append to the linked list
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while (start = strstr(start, "mul(")) {
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start = start + 4;
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// confirm format %d,%d)
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if (confirm_numbers(start, memory + fLen))
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addInstruction(list, start);
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}
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// from each instruction start, parse and mult numbers
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struct instruction *current = list;
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while (current) {
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sum += parse_numbers(current->coord);
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current = current->next;
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}
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printf("%d\n", sum);
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}
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