diff --git a/c++/KMP.cpp b/c++/KMP.cpp new file mode 100644 index 0000000..6d64ed4 --- /dev/null +++ b/c++/KMP.cpp @@ -0,0 +1,68 @@ +#include + +void computeLPSArray(char* pat, int M, int* lps); + +void KMPSearch(char* pat, char* txt) +{ + int M = strlen(pat); + int N = strlen(txt); + + int lps[M]; + computeLPSArray(pat, M, lps); + + int i = 0; + int j = 0; + while ((N - i) >= (M - j)) { + if (pat[j] == txt[i]) { + j++; + i++; + } + + if (j == M) { + printf("Found pattern at index %d ", i - j); + j = lps[j - 1]; + } + + else if (i < N && pat[j] != txt[i]) { + if (j != 0) + j = lps[j - 1]; + else + i = i + 1; + } + } +} +void computeLPSArray(char* pat, int M, int* lps) +{ + int len = 0; + + lps[0] = 0; // lps[0] is always 0 + + int i = 1; + while (i < M) { + if (pat[i] == pat[len]) { + len++; + lps[i] = len; + i++; + } + else // (pat[i] != pat[len]) + { + if (len != 0) { + len = lps[len - 1]; + + } + else // if (len == 0) + { + lps[i] = 0; + i++; + } + } + } +} + +int main() +{ + char txt[] = "ABABDABACDABABCABAB"; + char pat[] = "ABABCABAB"; + KMPSearch(pat, txt); + return 0; +}