Initial commit

4 files changed, 247 insertions, 0 deletions

diff --git a/2020/01/.gitignore b/2020/01/.gitignore
new file mode 100644
index 0000000..60d075d
--- /dev/null
+++ b/2020/01/.gitignore
@@ -0,0 +1 @@
+puzzle-[12]
diff --git a/2020/01/Makefile b/2020/01/Makefile
new file mode 100644
index 0000000..c32dafa
--- /dev/null
+++ b/2020/01/Makefile
@@ -0,0 +1,7 @@
+all:
+	${CC} ${CFLAGS} -o puzzle-1 puzzles.c
+	${CC} ${CFLAGS} -DPART2 -o puzzle-2 puzzles.c
+
+.PHONY: clean
+clean:
+	rm -f puzzle-[12]
diff --git a/2020/01/input b/2020/01/input
new file mode 100644
index 0000000..127b7a7
--- /dev/null
+++ b/2020/01/input
@@ -0,0 +1,200 @@
+1293
+1207
+1623
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+1842
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+85
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+1506
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diff --git a/2020/01/puzzles.c b/2020/01/puzzles.c
new file mode 100644
index 0000000..29384e0
--- /dev/null
+++ b/2020/01/puzzles.c
@@ -0,0 +1,39 @@
+#include <err.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#define BUFFER 200
+
+int
+main(void)
+{
+	int nums[BUFFER];
+	FILE *fp;
+
+	if (!(fp = fopen("input", "r")))
+		err(EXIT_FAILURE, "fopen");
+
+	for (int i = 0; i < BUFFER; i++)
+		fscanf(fp, "%d", &nums[i]);
+
+	fclose(fp);
+
+	/* Inefficient, but small sample size so it's fine */
+	for (int i = 0; i < BUFFER - 1; i++) {
+		for (int j = i + 1; j < BUFFER; j++) {
+#ifdef PART2
+			for (int k = j + 1; k < BUFFER; k++) {
+				if (nums[i] + nums[j] + nums[k] == 2020) {
+					printf("%d\n", nums[i] * nums[j] * nums[k]);
+					return EXIT_SUCCESS;
+				}
+			}
+#else
+			if (nums[i] + nums[j] == 2020) {
+				printf("%d\n", nums[i] * nums[j]);
+				return EXIT_SUCCESS;
+			}
+#endif
+		}
+	}
+}