[Lintcode] String lookup

Brute Force solution (O (MN)):

1 classSolution {2  Public:3     /**4 * Returns A index to the first occurrence of target in source,5 * or-1 If Target is no part of source.6 * @param source string to is scanned.7 * @param target string containing the sequence of characters to match.8      */9     intSTRSTR (Const Char*source,Const Char*target) {Ten         //Write your code here One         if(!source | |!target)return-1; A         intm = strlen (source), n =strlen (target); -          for(inti =0; I < M-n +1; i++) { -             intj =0, k =i; the              for(; J < N; j + +, k++) -                 if(Source[k]! =Target[j]) -                      Break; -             if(j = = N)returni; +         } -         return-1; +     } A};

KMP (O (M + N)):

1 classSolution {2  Public:3     /**4 * Returns A index to the first occurrence of target in source,5 * or-1 If Target is no part of source.6 * @param source string to is scanned.7 * @param target string containing the sequence of characters to match.8      */9     intSTRSTR (Const Char*source,Const Char*target) {Ten         //Write your code here One         if(!source | |!target)return-1; A         intm = strlen (source), n =strlen (target); -         if(!n)return 0; -vector<int> lps =kmpprocess (target, n); the          for(inti =0, j =0; I <m;) { -             if(Source[i] = =Target[j]) { -i++; -J + +; +             } -             if(j = = N)returnIJ; +             if(I < m && Source[i]! =Target[j]) { A                 if(j) J = lps[j-1]; at                 Elsei++; -             } -         } -         return-1; -     } - Private: invector<int> kmpprocess (Const Char* Target,intN) { -vector<int> LPs (N,0); to          for(inti =1, Len =0; I <N;) { +             if(Target[i] = =Target[len]) -lps[i++] = + +Len; the             Else if(len) len = Lps[len-1]; *             Elselps[i++] =0; $         }Panax Notoginseng         returnLPs; -     } the};

[Lintcode] String lookup