Merge pull request #232 from harshendram/Algo/KMP

Added the implmentation of KMP algorithm in cpp

Author: Pradeepsingh61

CPP/algorithms/searching/KMPalgorithm.cpp

@@ -0,0 +1,86 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+// Function to compute the LPS (Longest Prefix Suffix) array
+void computeLPSArray(const string &pattern, vector<int> &lps)
+{
+    int m = pattern.size();
+    int len = 0; // length of previous longest prefix suffix
+    lps[0] = 0;  // lps[0] is always 0
+
+    int i = 1;
+    while (i < m)
+    {
+        if (pattern[i] == pattern[len])
+        {
+            len++;
+            lps[i] = len;
+            i++;
+        }
+        else
+        {
+            if (len != 0)
+            {
+                len = lps[len - 1];
+            }
+            else
+            {
+                lps[i] = 0;
+                i++;
+            }
+        }
+    }
+}
+
+// KMP Search function
+void KMPSearch(const string &text, const string &pattern)
+{
+    int n = text.size();
+    int m = pattern.size();
+
+    vector<int> lps(m);
+    computeLPSArray(pattern, lps);
+
+    int i = 0; // index for text
+    int j = 0; // index for pattern
+    while (i < n)
+    {
+        if (pattern[j] == text[i])
+        {
+            i++;
+            j++;
+        }
+
+        if (j == m)
+        {
+            cout << "Pattern found at index " << (i - j) << endl;
+            j = lps[j - 1]; // Move pattern index based on lps
+        }
+        else if (i < n && pattern[j] != text[i])
+        {
+            if (j != 0)
+            {
+                j = lps[j - 1];
+            }
+            else
+            {
+                i++;
+            }
+        }
+    }
+}
+
+int main()
+{
+    string text, pattern;
+
+    cout << "Enter the text: ";
+    getline(cin, text);
+
+    cout << "Enter the pattern: ";
+    getline(cin, pattern);
+
+    KMPSearch(text, pattern);
+
+    return 0;
+}