Comparing strings and get the first place where they vary from eachother
string str1 = "AAAB";
string str2 = "AAAAC";
// returns the first difference index if found, or -1 if there's
// no difference, or if one string is contained in the other
public static int GetFirstDiffIndex(string str1, string str2)
{
if (str1 == null || str2 == null) return -1;
int length = Math.Min(str1.Length, str2.Length);
for (int index = 0; index < length; index++)
{
if (str1[index] != str2[index])
{
return index;
}
}
return -1;
}
/// <summary>
/// Compare two strings and return the index of the first difference. Return -1 if the strings are equal.
/// </summary>
int DiffersAtIndex(string s1, string s2)
{
int index = 0;
int min = Math.Min(s1.Length, s2.Length);
while (index < min && s1[index] == s2[index])
index++;
return (index == min && s1.Length == s2.Length) ? -1 : index;
}
static void Main(string[] args)
{
Console.WriteLine("enter s1 :");
string s1 = Console.ReadLine();
Console.WriteLine("enter s2 :");
string s2 = Console.ReadLine();
Console.WriteLine("note: zero means there is *no* first dif index starting from s1 ");
Console.WriteLine("first dif index of s1 :{0}", findFirstDifIndex(s1, s2)+1);
}
private static int findFirstDifIndex(string s1, string s2)
{
for (int i = 0; i <Math.Min(s1.Length, s2.Length); i++)
if (s1[i] != s2[i])
return i;
return -1;
}
.NET 4:
string a1 = "AAAB";
string a2 = "AAAAC";
int index = a1.Zip(a2, (c1, c2) => c1 == c2).TakeWhile(b => b).Count() + 1;