feat: initial version

srcs/ft_atoi.c

@@ -0,0 +1,29 @@
+#include "libft.h"
+
+int ft_atoi(const char *str)
+{
+    int i = 0;
+    int r = 0;
+    int s = 1;
+
+    while (str[i] == ' ' || (str[i] >= '\t' && str[i] <= '\r'))
+        i++;
+
+    if (str[i] == '-')
+    {
+        s = -1;
+        i++;
+    }
+    else if (str[i] == '+')
+        i++;
+    
+    while(str[i] != '\0')
+    {
+        if (str[i] >= '0' && str[i] <= '9')
+            r = r * 10 + str[i] - '0';
+        else
+            break;
+        i++;
+    }
+    return (s * r);
+}