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76 changes: 76 additions & 0 deletions KMP_algorithm/KMP_algorithm.cpp
Original file line number Diff line number Diff line change
@@ -0,0 +1,76 @@

#include <bits/stdc++.h>

void computeLPS(char* pat, int M, int* lps)
{

int len = 0;

lps[0] = 0;


int i = 1;
while (i < M) {
if (pat[i] == pat[len]) {
len++;
lps[i] = len;
i++;
}
else
{

if (len != 0) {
len = lps[len - 1];


}
else
{
lps[i] = 0;
i++;
}
}
}
}

void KMP(char* pat, char* txt)
{
int M = strlen(pat);
int N = strlen(txt);


int lps[M];

computeLPS(pat, M, lps);

int i = 0;
int j = 0;
while (i < N) {
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;
}
}
}




int main()
{
char txt[] = "ABABDABACDABABCABAB";
char pat[] = "ABABCABAB";
KMP(pat, txt);
return 0;
}