From 06f16eb09a9de96f1e18e575f2b5a7891e4e916d Mon Sep 17 00:00:00 2001
From: S R Pranav Suriya <91081814+pranavsuriya-sr@users.noreply.github.com>
Date: Sun, 9 Oct 2022 15:00:55 +0530
Subject: [PATCH 1/2] Add files via upload

---
 String/PatternMatching/KMPalgorithm.c++       | 85 +++++++++++++++++++
 String/PatternMatching/RabinKarpAlgorithm.c++ | 56 ++++++++++++
 2 files changed, 141 insertions(+)
 create mode 100644 String/PatternMatching/KMPalgorithm.c++
 create mode 100644 String/PatternMatching/RabinKarpAlgorithm.c++

diff --git a/String/PatternMatching/KMPalgorithm.c++ b/String/PatternMatching/KMPalgorithm.c++
new file mode 100644
index 0000000..3425ef3
--- /dev/null
+++ b/String/PatternMatching/KMPalgorithm.c++
@@ -0,0 +1,85 @@
+#include "bits/stdc++.h"
+using namespace std;
+
+void findLpsArray(char* pattern, int* lps, int m) 
+{
+    
+    int len = 0;
+  
+    lps[0] = 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++;
+            }
+        }
+    }
+}
+
+void patternSearchKMP(char* pattern, char* text) 
+{
+    int m = strlen(pattern);
+    int n = strlen(text);
+  
+    int lps[m]; //longest-prefix-suffix array
+    
+    findLpsArray(pattern, lps, m); //calling findLpsArray function
+  
+    int i = 0; 
+    int j = 0;
+    
+    while (i < n) 
+    {
+        if (pattern[j] == text[i]) 
+        {
+            j++;
+            i++;
+        }
+  
+        if (j == m) 
+        {
+            cout<<"Pattern found at index: "<<i - j;
+            j = lps[j - 1];
+        }
+        
+        else if (i < n && pattern[j] != text[i]) 
+        {
+            if (j != 0)
+                j = lps[j - 1];
+            else
+                i = i + 1;
+        }
+    }
+}
+  
+int main()
+{
+    char pattern[100], text[100];
+    
+    cout<<"Enter the pattern to be found: "<<endl;
+    cin>>pattern;
+    
+    cout<<"Enter the string in which the pattern is to be found: "<<endl;
+    cin>>text;
+    
+    patternSearchKMP(pattern, text); //Function call
+    
+    return 0;
+}
+
diff --git a/String/PatternMatching/RabinKarpAlgorithm.c++ b/String/PatternMatching/RabinKarpAlgorithm.c++
new file mode 100644
index 0000000..ccef543
--- /dev/null
+++ b/String/PatternMatching/RabinKarpAlgorithm.c++
@@ -0,0 +1,56 @@
+#include "bits/stdc++.h"
+using namespace std;
+
+void rabinKarpAlgo(char* text, char* pattern)
+{
+    int m = strlen(text);
+    int n = strlen(pattern);
+    
+    int prime = 31;
+    int mod = 1e9 + 9;
+    
+    vector<long long> p_pow(m);
+    p_pow[0] = 1; 
+    
+    for (int i = 1; i < m; i++) 
+    {
+        p_pow[i] = (p_pow[i-1] * prime) % mod;
+    }
+       
+    vector<long long> h(m + 1, 0); 
+    
+    for (int i = 0; i < m; i++)
+    {
+        h[i+1] = (h[i] + (text[i] - 'a' + 1) * p_pow[i]) % mod;
+    }
+    
+    long long hash_pattern = 0; 
+    
+    for (int i = 0; i < n; i++) 
+    {
+        hash_pattern = (hash_pattern + (pattern[i] - 'a' + 1) * p_pow[i]) % mod; 
+    }
+      
+    for (int i = 0; i + n - 1 < m; i++) 
+    { 
+        long long curr_hash = (h[i+n] + mod - h[i]) % mod; 
+        
+        if (curr_hash == hash_pattern * p_pow[i] % mod)
+            cout<<"Pattern found at index: "<<i<<endl;
+    }
+}
+
+int main()
+{
+    char pattern[100], text[100];
+    
+    cout<<"Enter the pattern to be found: "<<endl;
+    cin>>pattern;
+    
+    cout<<"Enter the string in which the pattern is to be found: "<<endl;
+    cin>>text;
+    
+    rabinKarpAlgo(text, pattern); //Function call
+    
+    return 0;
+}

From 828b051a3bace969c1d076a4b361334cc46b4afc Mon Sep 17 00:00:00 2001
From: S R Pranav Suriya <91081814+pranavsuriya-sr@users.noreply.github.com>
Date: Sun, 9 Oct 2022 15:21:10 +0530
Subject: [PATCH 2/2] Create README.md

---
 String/PatternMatching/README.md | 40 ++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)
 create mode 100644 String/PatternMatching/README.md

diff --git a/String/PatternMatching/README.md b/String/PatternMatching/README.md
new file mode 100644
index 0000000..032333f
--- /dev/null
+++ b/String/PatternMatching/README.md
@@ -0,0 +1,40 @@
+KMP Algorithm:
+
+The Knuth-Morris-Pratt algorithm is used to find a given text from a specific word. 
+
+This algorithm uses the degenerating property which primarily works based on sub-strings. 
+
+The basic idea of this algorithm is to not match a character which is already known to match for sure.
+
+Example:
+
+Output: Enter the pattern to be found:
+
+Input: cktober
+
+Output : Enter the string in which the pattern is to be found: 
+
+Input: hacktoberfest
+
+Output/Answer: Pattern found at index: 2
+
+Rabin Karp Algorithm
+
+The Rabin karp Algorithm is used to search a text from a given word using hash function.
+
+This algorithm doesnt search slide through every character but filters the unlike characters and then does the comparing.
+
+Example:
+
+Enter the pattern to be found: 
+
+program
+
+Enter the string in which the pattern is to be found: 
+
+competitveprogramming
+
+Pattern found at index: 10
+
+
+