From 04e79fa276ae1c3620868d85941b2c7b7c11222a Mon Sep 17 00:00:00 2001
From: Vincent Douillet <vincent@vdouillet.fr>
Date: Fri, 3 Dec 2021 14:09:39 +0100
Subject: day 3

---
 .gitignore |  2 ++
 03.c       | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 Makefile   |  5 ++++-
 3 files changed, 61 insertions(+), 1 deletion(-)
 create mode 100644 03.c

diff --git a/.gitignore b/.gitignore
index 54be510..4cbdfc9 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,6 @@
+??
 ???
 *.o
 input/
 *.swp
+answer.csv
diff --git a/03.c b/03.c
new file mode 100644
index 0000000..02af910
--- /dev/null
+++ b/03.c
@@ -0,0 +1,55 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <err.h>
+#include <string.h>
+#include "input.h"
+
+#define INPUT "input/03.txt"
+#define INPUT_SIZE 12
+
+void part1(char** input, size_t lineCount) {
+	int oneCount[INPUT_SIZE];
+	for(int k = 0; k < INPUT_SIZE; k++) {
+		oneCount[k] = 0;
+	}
+
+	for(size_t i = 0; i < lineCount; i++) {
+		char* line = input[i];
+		for(int j = 0; j < INPUT_SIZE; j++) {
+			if(line[j] == '1')
+				oneCount[j]++;
+		}
+	}
+
+	// null terminated string	
+	char binary[INPUT_SIZE + 1];
+	for(int h = 0; h < INPUT_SIZE; h++) {
+		binary[h] = oneCount[h] > lineCount / 2.0f ? '1' : '0';
+	}
+	binary[INPUT_SIZE] = '\0';
+	char* endp = NULL;
+	unsigned long gamma = strtoul(binary, &endp, 2);
+	unsigned long epsilon = gamma ^ 0xFFF;
+	if(*endp != '\0')
+		err(1, "erreur de parsing du gammaat");
+
+	printf("%ld\n", gamma * epsilon);
+}
+
+int main() {
+	// lecture du fichier d'entree
+	FILE* file=fopen(INPUT,"r");
+	if(file == NULL)
+		err(1, "Le fichier %s n'existe pas\n", INPUT);
+	
+	size_t lineCount = count_lines(file);
+	char** input = malloc(lineCount * sizeof(char*));
+	read_lines_as_string(file, input, lineCount);
+	// fermeture du fichier
+	fclose(file);
+
+	part1(input, lineCount);
+
+	free_strings(input, lineCount);
+	return 0;
+}
diff --git a/Makefile b/Makefile
index 1a2b7e9..baca8e6 100644
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,7 @@
 CC=cc
 CFLAGS=-std=c1x -W -Wall -g
 LDFLAGS=
-EXEC=011 012 021 022
+EXEC=011 012 021 022 03
 
 all: $(EXEC)
 
@@ -17,6 +17,9 @@ all: $(EXEC)
 022: input.o 022.o
 	$(CC) -o $@ $> $(LDFLAGS)
 
+03: input.o 03.o
+	$(CC) -o $@ $> $(LDFLAGS)
+
 .c.o:
 	$(CC) -o $@ -c $< $(CFLAGS)
 
-- 
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