2020/day14.c


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#include <stdio.h>
#include <stdlib.h>
typedef unsigned long ul;
static struct {
	ul addr;
	ul val;
} writes[1024];
static int len;
static void write(ul addr, ul val) {
	for (int i = 0; i < len; ++i) {
		if (writes[i].addr == addr) {
			writes[i].val = val;
			return;
		}
	}
	writes[len].addr = addr;
	writes[len++].val = val;
}
int main(void) {
	ul mask = 0;
	ul bits = 0;
	for (;;) {
		char str[37];
		int n = scanf("mask = %s\n", str);
		if (n < 0) break;
		if (n) {
			mask = 0;
			bits = 0;
			for (ul i = 35; i < 36; --i) {
				if (str[35-i] == 'X') {
					mask |= 1UL << i;
				} else if (str[35-i] == '1') {
					bits |= 1UL << i;
				}
			}
		} else {
			ul addr, val;
			n = scanf("em[%lu] = %lu\n", &addr, &val);
			if (n < 2) break;
			val &= mask;
			val |= bits;
			write(addr, val);
		}
	}
	ul sum = 0;
	for (int i = 0; i < len; ++i) {
		sum += writes[i].val;
	}
	printf("%lu\n", sum);
}