String Matching Algo: KMP (knuth Morris Pratt) Algo'

Author: Faisal786111

Algorithms/String Matching/KMP/input.txt

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+5 3
+4 0 3 -12 1

Algorithms/String Matching/KMP/main.c

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+#include <stdio.h>
+#include <string.h>
+
+void computeLPS(char *P, int m, int *lps){
+    // 0th index letter always set to 0
+    lps[0] = 0;
+    int k = 0;
+
+    for(int q = 1; q < m; q++){
+        // Compare P with P until k > 0;
+        while(k > 0 && P[q] != P[k]){
+            k = lps[k-1];
+        }
+
+        // If match
+        if(P[q] == P[k]){
+            // Increment k value
+            k++;
+        }
+
+        // Store in lps 
+        lps[q] = k;
+    }
+}
+
+int main(){
+    char str[] = "ababcabcabababd";
+    int n = strlen(str);
+    
+    char P[] = "ababd";
+    int m = strlen(P);
+
+    int lps[m];
+    computeLPS(P, m, lps);
+
+    printf("LPS array:\n");
+    for (int i = 0; i < m; i++) {
+        printf("%d ", lps[i]);
+    }
+
+    int q = 0;
+    // Now apply KMP algo 
+    for (int i = 0; i < n; i++) {
+        while (q > 0 && str[i] != P[q]) {
+            q = lps[q - 1];
+        }
+
+        if (str[i] == P[q]) {
+            q++;
+        }
+
+        if (q == m) {
+            printf("Pattern found at index %d\n", i - m + 1);
+            q = lps[q - 1]; // To continue searching for next occurrence
+        }
+    }
+
+    return 0;
+}

Algorithms/String Matching/KMP/main.exe

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+0-12-12