Find common char(s) from two string.

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Hi,
For example, there is two string:

string str1 = "abcde";
string str2 = "abccc";

The common chars are:
a, b, c from str1, and a, b, c, c, c from str2.
So, the sum of these common char(s) is 3 + 5 = 8.
Could someone show me a function that can do this?

public int FindCommonChars(string str1, string str2)
{
....
}

I have written one 2x nested loop, but it seems very ... (you know)
/*

int i = 0;
foreach(char c1 in str1)
{
foreach(char c2 in str 2)
{
if(c1 == c2) i++;
}
}
foreach (char c2 in str 2)
{
foreach(char c1 in str1)
{
if(c2 == c1) i++;
}
}
return i;

*/
T_T, the Questioner very very contempt my answer:(

Posted 11-May-10 23:42pm

andersonhwang

Updated 11-May-10 23:45pm

v2

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#realJSOP · Answer 1 · 2010-05-11T23:54:00

Solution 1

Use a hashtable that contains the unique characters from string 1, and then you only need to try adding characters from string 2 and count the number of times you get an exception (happens when you try to add an item that already exists in the hashtable).

That's the first way I thought of. You could also probably use Linq or regex.

You could even reduce it to just one loop.

Posted 11-May-10 23:54pm

#realJSOP

Comments

andersonhwang 12-May-10 6:21am

Hi, John
Do you mean this:
public static int FindCommonChars(string str1, string str2)
{
Hashtable hTable = new Hashtable();
int i = 0;
foreach (char c in str1)
{
if (!hTable.Contains(c))
{
hTable.Add(c, c);
}
}
foreach (char c in str2)
{
try
{
hTable.Add(c, c);
}
catch (Exception ex)
{
i++;
continue;
}
}
return i;
}
but it will return 5, not 8.

CPallini · Answer 2 · 2010-05-12T00:29:00

C#

static int common(string s1, string s2)
    {
        int count = 0;
        byte [] a = new byte[26];
        byte [] b  = new byte[26];
        foreach(char c in s1)
            a[c - 'a']++;
        foreach (char c in s2)
            b[c - 'a']++;
        for (int i = 0; i < 26; i++)
        {
            if (a[i] != 0 && b[i] != 0) count += a[i] + b[i];
        }
        return count;
    }

:-)

andersonhwang · Answer 3 · 2010-05-12T19:05:00

Solution 3

My senior show me one function that is:

C#

char[] ch1 = str1.ToCharArray();
char[] ch2 = str2.ToCharArray();

var p1 = ch1.Except(ch2);
var p2 = ch2.Except(ch1);
int count=(ch1.Length-p1.Count())+ (ch2.Length-p2.Count());

Posted 12-May-10 19:05pm