# C++ Program to Find the Longest Prefix Matching of a Given Sequence

Here we shall discuss a C++ program to find the Longest Subsequence Common to All Sequences in a Set of Sequences.

## Algorithms

Begin
Take the array of strings as input.
function matchedPrefixtill(): find the matched prefix between string s1 and s2 :
n1 = store length of string s1.
n2 = store length of string s2.
for i = 0, j = 0 to i <= n1 – 1 && j <= n2 - 1
if s1[i] != s2[j]
break
result.push_back(s1[i])
return result
End
Begin
function matchedPrefix(): returns the longest matched prefix from the array of strings:
for int i = 1 to n - 1
pre = matchedPrefixtill(pre, a[i])
return pre.
End

## Example

#include<bits/stdc++.h>
using namespace std;
string matchedPrefixtill(string s1, string s2) {
string res;
int n1 = s1.length(); //store length of string s1.
int n2 = s2.length(); //store length of string s2.
for (int i = 0, j = 0; i <= n1 - 1 && j <= n2 - 1; i++, j++) {
if (s1[i] != s2[j])
break;
res.push_back(s1[i]);
}
return (res);
}
string matchedPrefix (string a[], int n) {
string pre = a;
for (int i = 1; i <= n - 1; i++)
pre = matchedPrefixtill(pre, a[i]);
return (pre);
}
int main() {
string a[] = {"Tutorialspoint", "Tutor", "Tutorials"}; //taking inputs
int n = sizeof(a) / sizeof(a);
string res = matchedPrefix(a, n);
if (res.length())
cout<<"Longest common subsequence is matched - "<<res.c_str();
else
cout<<"No matched prefix";
return (0);
}

## Output

Longest common subsequence is matched - Tutor