Search string pattern in string

Question

if I have string let say "abcddgert234edddscddvbasdeddd" and if I want to search a pattern "ddd" what would be the raw logic?

Some sort of String searching algorithm

Answer 1

There is no raw logic. Although i did see the pcre inner workings presentation somewhere on the web.

Answer 2

The simplest thing is to go over the string, start to end. You can find such sequences easily enough.

Using a regex, you can try (.)\1{2,} - this searches for sequences of three or more of the same character. Not all regex flavors allow this - it depends on your language.

Answer 3

Raw searching alogs

http://en.wikipedia.org/wiki/String%5Fsearching%5Falgorithm

simplest one

bool flag = false;
    for(int i=0;i<=text.length;i++)
    {
     if(text[i]==stringToBeSearched[0])
     {
      flag=true;
       for(j=1;j<=stringToBeSearched.length;j++)
       {
         if(text[i]==stringToBeSearched[j])
         {
         i++;
         flag=true;
         }
         else
         {
         flag=false;
         break;
         }
       }
     }
    }

It is a pseudocode and it might need some optimization.

Answer 4

you should clearly defined what is "ddd". Depending on what you use, it might be just passing this "ddd" string to a "parser", eg grep

grep "ddd" file

or languages with regex syntax,

perl -ne 'print if (/ddd/)' file

otherwise, if its really RAW logic you want, ie, go through the string 1 char by 1 char

for each char in string
    if char is "d":
        if check next char is "d":
             if check next char is "d":
                  print "found"

Answer 5

Python.

mystr="abcddgert234edddscddvbasdeddd"
for num,ch in enumerate(mystr):    
    try:
        if ch == "d":
            if mystr[num+1] == "d" :
                if mystr[num+2] == "d":
                    print "found ddd at position: ",num
    except:pass