1 files changed, 71 insertions, 0 deletions
diff --git a/04.c b/04.c
new file mode 100644
index 0000000..dfb653b
--- /dev/null
+++ b/04.c
@@ -0,0 +1,71 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <err.h>
+#include <string.h>
+#include "input.h"
+
+#define INPUT "input/04.txt"
+#define EXPECTED1 573L
+#define EXPECTED2 867L
+
+void part1(struct input_str* input) {
+	size_t overlap_count = 0;
+	int section_range[4];
+	for(size_t i = 0; i < input->line_count; i++) {
+		// strtok will butcher our line, so give it a copy!
+		char* line = copy_line(input->lines[i]);
+		for(int a = 0; a < 4; a++) {
+			char* section = NULL;
+			if(a == 0)
+				section = strtok(line, "-,");
+			else
+				section = strtok(NULL, "-,");
+
+			section_range[a] = atoi(section);
+		}
+		free(line);
+		line = NULL;
+		// check range inclusion
+		if((section_range[0] <= section_range[2] && section_range[1] >= section_range[3]) || (section_range[2] <= section_range[0] && section_range[3] >= section_range[1]))
+			overlap_count++;
+	}
+	CHECK(overlap_count, EXPECTED1)
+}
+
+void part2(struct input_str* input) {
+	size_t overlap_count = 0;
+	int section_range[4];
+	for(size_t i = 0; i < input->line_count; i++) {
+		// strtok will butcher our line, so give it a copy!
+		char* line = copy_line(input->lines[i]);
+		for(int a = 0; a < 4; a++) {
+			char* section = NULL;
+			if(a == 0)
+				section = strtok(line, "-,");
+			else
+				section = strtok(NULL, "-,");
+
+			section_range[a] = atoi(section);
+		}
+		free(line);
+		line = NULL;
+		// check range overlap
+		if((section_range[2] <= section_range[1] && section_range[3] >= section_range[0]) || (section_range[0] <= section_range[3] && section_range[1] >= section_range[2]))
+			overlap_count++;
+	}
+	CHECK(overlap_count, EXPECTED2)
+}
+
+int main() {
+	// read input
+	struct input_str input;
+	input_str_read(&input, INPUT);
+
+	// do stuff
+	part1(&input);
+	part2(&input);
+
+	// cleanup & exit
+	input_str_free(&input);
+	return 0;
+}