2019/day05.c


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#include <stdio.h>
#include <stdlib.h>

static int input(void) {
	return 1;
}

static void output(int x) {
	printf("%d\n", x);
}

static int ip;
static int mem[1024];

static int *p(int mode, int param) {
	return (mode ? &mem[ip + param] : &mem[mem[ip + param]]);
}

static void run(void) {
	while (mem[ip] != 99) {
		int op = mem[ip] % 100;
		int m1 = mem[ip] / 100 % 10;
		int m2 = mem[ip] / 1000 % 10;
		int m3 = mem[ip] / 10000 % 10;
		switch (op) {
			break; case 1: *p(m3, 3) = *p(m1, 1) + *p(m2, 2); ip += 4;
			break; case 2: *p(m3, 3) = *p(m1, 1) * *p(m2, 2); ip += 4;
			break; case 3: *p(m1, 1) = input(); ip += 2;
			break; case 4: output(*p(m1, 1)); ip += 2;
			break; default: abort();
		}
	}
}

int main(void) {
	for (int i = 0; EOF != scanf("%d,", &mem[i]); ++i);
	run();
}