1 files changed, 112 insertions, 0 deletions
diff --git a/2018/day19.c b/2018/day19.c
new file mode 100644
index 0000000..5802ffa
--- /dev/null
+++ b/2018/day19.c
@@ -0,0 +1,112 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+typedef unsigned uint;
+
+struct CPU {
+	uint ip;
+	uint r[6];
+};
+
+typedef struct CPU Op(struct CPU, uint, uint, uint);
+
+static struct CPU addr(struct CPU cpu, uint a, uint b, uint c) {
+	cpu.r[c] = cpu.r[a] + cpu.r[b]; return cpu;
+}
+static struct CPU addi(struct CPU cpu, uint a, uint b, uint c) {
+	cpu.r[c] = cpu.r[a] + b; return cpu;
+}
+static struct CPU mulr(struct CPU cpu, uint a, uint b, uint c) {
+	cpu.r[c] = cpu.r[a] * cpu.r[b]; return cpu;
+}
+static struct CPU muli(struct CPU cpu, uint a, uint b, uint c) {
+	cpu.r[c] = cpu.r[a] * b; return cpu;
+}
+static struct CPU banr(struct CPU cpu, uint a, uint b, uint c) {
+	cpu.r[c] = cpu.r[a] & cpu.r[b]; return cpu;
+}
+static struct CPU bani(struct CPU cpu, uint a, uint b, uint c) {
+	cpu.r[c] = cpu.r[a] & b; return cpu;
+}
+static struct CPU borr(struct CPU cpu, uint a, uint b, uint c) {
+	cpu.r[c] = cpu.r[a] | cpu.r[b]; return cpu;
+}
+static struct CPU bori(struct CPU cpu, uint a, uint b, uint c) {
+	cpu.r[c] = cpu.r[a] | b; return cpu;
+}
+static struct CPU setr(struct CPU cpu, uint a, uint b, uint c) {
+	cpu.r[c] = cpu.r[a]; return cpu;
+}
+static struct CPU seti(struct CPU cpu, uint a, uint b, uint c) {
+	cpu.r[c] = a; return cpu;
+}
+static struct CPU gtir(struct CPU cpu, uint a, uint b, uint c) {
+	cpu.r[c] = a > cpu.r[b]; return cpu;
+}
+static struct CPU gtri(struct CPU cpu, uint a, uint b, uint c) {
+	cpu.r[c] = cpu.r[a] > b; return cpu;
+}
+static struct CPU gtrr(struct CPU cpu, uint a, uint b, uint c) {
+	cpu.r[c] = cpu.r[a] > cpu.r[b]; return cpu;
+}
+static struct CPU eqir(struct CPU cpu, uint a, uint b, uint c) {
+	cpu.r[c] = a == cpu.r[b]; return cpu;
+}
+static struct CPU eqri(struct CPU cpu, uint a, uint b, uint c) {
+	cpu.r[c] = cpu.r[a] == b; return cpu;
+}
+static struct CPU eqrr(struct CPU cpu, uint a, uint b, uint c) {
+	cpu.r[c] = cpu.r[a] == cpu.r[b]; return cpu;
+}
+
+static const struct {
+	const char *name;
+	Op *fn;
+} Ops[16] = {
+	{ "addr", addr },
+	{ "addi", addi },
+	{ "mulr", mulr },
+	{ "muli", muli },
+	{ "banr", banr },
+	{ "bani", bani },
+	{ "borr", borr },
+	{ "bori", bori },
+	{ "setr", setr },
+	{ "seti", seti },
+	{ "gtir", gtir },
+	{ "gtri", gtri },
+	{ "gtrr", gtrr },
+	{ "eqir", eqir },
+	{ "eqri", eqri },
+	{ "eqrr", eqrr },
+};
+
+int main(void) {
+	struct CPU cpu = { .r = { 0, 0, 0, 0, 0, 0 } };
+	scanf("#ip %u\n", &cpu.ip);
+
+	uint len = 0;
+	struct Ins {
+		char op[4];
+		uint a, b, c;
+	} prog[50];
+	while (!feof(stdin)) {
+		scanf(
+			"%4c %u %u %u\n",
+			prog[len].op, &prog[len].a, &prog[len].b, &prog[len].c
+		);
+		len++;
+	}
+
+	while (cpu.r[cpu.ip] < len) {
+		struct Ins ins = prog[cpu.r[cpu.ip]];
+		for (uint i = 0; i < 16; ++i) {
+			if (strncmp(ins.op, Ops[i].name, 4)) continue;
+			cpu = Ops[i].fn(cpu, ins.a, ins.b, ins.c);
+			cpu.r[cpu.ip]++;
+			break;
+		}
+	}
+	printf("%u\n", cpu.r[0]);
+}