//REVERSE THE GIVEN STRING AND FIND LONGEST COMMON SUBSEQUENCE(LCS) 

#include <bits/stdc++.h>
using namespace std;

int main() 
{
    string a; cin>>a;
    
    string b = a;
    reverse(a.begin(),a.end());
    
    int n = a.size();
    int m = b.size();
    
    int dp[n+1][m+1];
    
    for(int i=0; i<=n; i++)
    {
      for(int j=0; j<=m ; j++)
      {
        if(i==0 || j==0) dp[i][j] = 0; //if(n=0 | m=0) return 0;
      }
    }
    
    for(int i=1; i<=n; i++)
    {
      for(int j=1; j<=m; j++)
      {
        if(a[i-1] == b[j-1]) dp[i][j] = 1 + dp[i-1][j-1];
        else{
          dp[i][j] = max(dp[i-1][j],dp[i][j-1]);
        }
      }
    }
    
    cout<<dp[n][m]<<endl;
    
    //print the palindrome
    string ans ;
    while(n!=0 && m!=0)
    {
      if(a[n-1] == b[m-1]) 
      {
        ans += a[n-1];
        n--; m--;
      }
      
      else if(dp[n-1][m] > dp[n][m-1]) //up
      {
        n--;
      }
      else//left
      {
        m--;
      }
    }
    
    reverse(ans.begin(),ans.end());
    cout<<ans<<endl;
    return 0;
}
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#include <iostream>
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    cout << "Enter name:";
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    cout << "Hello " << name;
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About C++

C++ is a widely used middle-level programming language.

  • Supports different platforms like Windows, various Linux flavours, MacOS etc
  • C++ supports OOPS concepts like Inheritance, Polymorphism, Encapsulation and Abstraction.
  • Case-sensitive
  • C++ is a compiler based language
  • C++ supports structured programming language
  • C++ provides alot of inbuilt functions and also supports dynamic memory allocation.
  • Like C, C++ also allows you to play with memory using Pointers.

Syntax help

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition If-Else is used.

if(conditional-expression) {
   //code
}
else {
   //code
}

You can also use if-else for nested Ifs and If-Else-If ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to If-Else-If ladder.

switch(conditional-expression){    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
......    
    
default:     
 code to be executed when all the above cases are not matched;    
}

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement){  
  //code  
}

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while (condition) {  
// code 
}

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {  
 // code 
} while (condition);

Functions

Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity. Function gets run only when it is called.

How to declare a Function:

return_type function_name(parameters);

How to call a Function:

function_name (parameters)

How to define a Function:

return_type function_name(parameters) {  
 // code
}