Algorithm For Brute-Force String matching

1. i = 1; [ substring 1]
2. Repeat steps 3 to 5 while i <=n-m+1 do
3. for j= 1 to m [For each character of P]

   If P[j] != T[i+j-1] then
   goto step 5

4. Print "Pattern found at shift i "
5. i= i + 1
6. exit

• The complexity of the brute force string matching algorithm is O(nm)
• On average the inner loop runs fewer than m times to know that there is a mismatch.
• The worst case situation arises when first m character are matched for all substrings S_i. If pattern is of the a^m-1b and text is of the form a^n-1b, where a^n-1 denotes a repeated n -1 times. In this case the inner loop runs exactly for m times before knowing that there is a mismatch. In this situation there will be exactly m*(n-m+1) number of comparisons.