131 lines
2.5 KiB
C
131 lines
2.5 KiB
C
#include <stdbool.h>
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#include <stddef.h>
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#include "parse.h"
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#include "printf.h"
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struct mul
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{
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int x;
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int y;
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};
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enum instruction_type {
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INSTRUCTION_MUL,
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INSTRUCTION_DO,
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INSTRUCTION_DONT,
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};
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struct instruction {
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enum instruction_type type;
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struct mul mul;
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};
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const char * parse_instruction(const char * input, const char * end, struct instruction * ins)
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{
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while (input < end) {
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const char * mdo = parse_match(input, "do()");
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if (mdo != NULL) {
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ins->type = INSTRUCTION_DO;
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return mdo;
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}
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const char * mdont = parse_match(input, "don't()");
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if (mdont != NULL) {
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ins->type = INSTRUCTION_DONT;
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return mdont;
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}
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const char * m = parse_match(input, "mul(");
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if (m == NULL) {
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input++;
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continue;
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}
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input = m;
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const char * x = parse_base10(input, &ins->mul.x);
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if (x == input) continue;
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input = x;
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if (ins->mul.x < 0 || ins->mul.x > 999) continue;
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const char * c = parse_match(input, ",");
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if (c == NULL) continue;
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input = c;
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const char * y = parse_base10(input, &ins->mul.y);
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if (y == input) continue;
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input = y;
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if (ins->mul.y < 0 || ins->mul.y > 999) continue;
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const char * p = parse_match(input, ")");
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if (p == NULL) continue;
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input = p;
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ins->type = INSTRUCTION_MUL;
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return input;
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}
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return NULL;
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}
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int parse_input(const char * input, int length, struct instruction * ins)
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{
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const char * end = input + length;
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int i = 0;
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while (true) {
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if (i >= 1000) {
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printf("error: ins limit exceeded\n");
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return 0;
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}
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input = parse_instruction(input, end, &ins[i]);
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if (input == NULL)
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break;
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i += 1;
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}
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return i;
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}
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int day3_part1(const char * input, int length)
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{
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struct instruction ins[1000];
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int mul_length = parse_input(input, length, ins);
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int sum = 0;
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for (int i = 0; i < mul_length; i++) {
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if (ins[i].type == INSTRUCTION_MUL)
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sum += ins[i].mul.x * ins[i].mul.y;
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}
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return sum;
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}
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int day3_part2(const char * input, int length)
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{
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struct instruction ins[1000];
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int mul_length = parse_input(input, length, ins);
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int mul_enabled = true;
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int sum = 0;
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for (int i = 0; i < mul_length; i++) {
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switch (ins[i].type) {
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case INSTRUCTION_MUL:
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if (mul_enabled)
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sum += ins[i].mul.x * ins[i].mul.y;
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break;
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case INSTRUCTION_DO:
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mul_enabled = true;
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break;
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case INSTRUCTION_DONT:
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mul_enabled = false;
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break;
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}
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}
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return sum;
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}
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