ft_itoa: initial implementation

I wrote this in a single session, with 0 errors on the first try!

Makefile

@@ -6,7 +6,7 @@
 #    By: kcolin <marvin@42.fr>                      +#+  +:+       +#+         #
 #                                                 +#+#+#+#+#+   +#+            #
 #    Created: 2024/10/14 13:43:59 by kcolin            #+#    #+#              #
-#    Updated: 2024/10/17 14:12:23 by kcolin           ###   ########.fr        #
+#    Updated: 2024/10/17 17:07:32 by kcolin           ###   ########.fr        #
 #                                                                              #
 # **************************************************************************** #
 
@@ -38,7 +38,8 @@ SOURCES = ft_isalpha.c \
 	ft_substr.c \
 	ft_strjoin.c \
 	ft_strtrim.c \
-	ft_split.c
+	ft_split.c \
+	ft_itoa.c
 OBJECTS = $(SOURCES:.c=.o)
 CC = gcc
 

ft_itoa.c

@@ -0,0 +1,73 @@
+/* ************************************************************************** */
+/*                                                                            */
+/*                                                        :::      ::::::::   */
+/*   ft_itoa.c                                          :+:      :+:    :+:   */
+/*                                                    +:+ +:+         +:+     */
+/*   By: kcolin <marvin@42.fr>                      +#+  +:+       +#+        */
+/*                                                +#+#+#+#+#+   +#+           */
+/*   Created: 2024/10/17 17:08:01 by kcolin            #+#    #+#             */
+/*   Updated: 2024/10/17 17:33:18 by kcolin           ###   ########.fr       */
+/*                                                                            */
+/* ************************************************************************** */
+
+#include "libft.h"
+#include <stdlib.h>
+
+static int	nb_needed_chars(long num)
+{
+	int	count;
+
+	count = 0;
+	if (num <= 0)
+	{
+		count++;
+		num = -num;
+	}
+	while (num != 0)
+	{
+		count++;
+		num /= 10;
+	}
+	return (count);
+}
+
+char	*ft_itoa(int n)
+{
+	long	num;
+	size_t	idx;
+	char	*out;
+
+	num = n;
+	idx = nb_needed_chars(num);
+	if (num < 0)
+		num = -num;
+	out = malloc(idx + 1);
+	if (out == NULL)
+		return (NULL);
+	out[idx--] = '\0';
+	while (num > 0)
+	{
+		out[idx--] = (num % 10) + '0';
+		num /= 10;
+	}
+	if (n < 0)
+		out[idx] = '-';
+	if (n == 0)
+		out[idx] = '0';
+	return (out);
+}
+
+/*
+#include <stdio.h>
+#include <limits.h>
+
+int	main(void)
+{
+	printf("%s\n", ft_itoa(0));
+	printf("%s\n", ft_itoa(42));
+	printf("%s\n", ft_itoa(-42));
+	printf("%s\n", ft_itoa(INT_MAX));
+	printf("%s\n", ft_itoa(INT_MIN));
+	return (0);
+}
+*/

libft.h

@@ -52,4 +52,6 @@ char	*ft_strjoin(char const *s1, char const *s2);
 char	*ft_strtrim(char const *s1, char const *set);
 char	**ft_split(char const *s, char c);
 
+char	*ft_itoa(int n);
+
 #endif