2020/day08.c


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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
static struct Ins {
	char op[4];
	int arg;
} prog[1024];
static int len;
static int acc;
static int pc;
static void step(void) {
	if (!strcmp(prog[pc].op, "acc")) {
		acc += prog[pc].arg;
	} else if (!strcmp(prog[pc].op, "jmp")) {
		pc += prog[pc].arg;
		return;
	}
	pc++;
}
static int terminates(void) {
	acc = 0;
	pc = 0;
	int ran[1024] = {0};
	while (!ran[pc]++ && pc < len) {
		step();
	}
	return pc == len;
}
int main(void) {
	while (EOF != scanf("%s %d\n", prog[len].op, &prog[len].arg)) {
		len++;
	}
	terminates();
	printf("%d\n", acc);
	for (int i = 0; i < len; ++i) {
		if (!strcmp(prog[i].op, "jmp")) {
			strcpy(prog[i].op, "nop");
			if (terminates()) break;
			strcpy(prog[i].op, "jmp");
		} else if (!strcmp(prog[i].op, "nop")) {
			strcpy(prog[i].op, "jmp");
			if (terminates()) break;
			strcpy(prog[i].op, "nop");
		}
	}
	printf("%d\n", acc);
}