Encryption using combination of Caesar and Transposition Algorithm

#include<iostream>
#include<string.h>
#include<cmath>
using namespace std;
int *keyfunctio(int n){
  int* ar = new int[n]; 
  cout<<"Enter the Key for 2nd Encryption: "<<endl;
  for(int i=0;i<n;i++){
    cin>>ar[i];
  }
  return ar;
}
string caesar(char msg[],int key){
  char ch;
      for(int i = 0; msg[i] != '\0'; ++i) {
         ch = msg[i];
         if(ch >= 'a' && ch <= 'z'){
            ch = ch + key;
            if (ch > 'z') {
              ch = ch - 'z' + 'a' - 1;
            }  
            msg[i] = ch;
         }
         else if (ch >= 'A' && ch <= 'Z'){
         	 ch = ch + key;
            if (ch > 'Z'){
               ch = ch - 'Z' + 'A' - 1;
            }
            msg[i] = ch;
         }
      }
      return msg;
}
void trans(string cipher, int key2, int arr[]){
  int col,j; 
  string cipher1 = ""; 
  col = key2;
  int length=cipher.size();
  int row =ceil((float)length/(float)col); 	
  char matrix[row][col]; 
  for (int i=0,k=0; i<row; i++) 
  { 
    for (int j=0; j<col; ) 
    { 
      if(cipher[k] == '\0' || cipher[k]==' ') 
      { 
        matrix[i][j] = '_';	 
        j++; 
      } 
      
      if( isalpha(cipher[k]) ) 
      { 
        matrix[i][j] = cipher[k]; 
        j++; 
      } 
      k++; 
    } 
  } 
  for(int i=0; i<row; i++){
    for(int j=0; j<col; j++){
      cout<<matrix[i][j]<<' ';
    }
    cout<<endl;
  }
  cout<<endl<<"The Encrypted Message is : ";
  for(int i=0;i<key2;i++){
    for(int j=0;j<row;j++){
      cout<<matrix[j][arr[i]-1];
    }
  
  }
  cout<<endl<<endl;
}
int main(){
  char ch[100];
  int n, k;
  cout<<"Enter the String : ";
  cin.getline(ch,100);
  cout<<"Enter the key for 1st encryption :"<<endl;
  cin>>k;
  string ch2 = caesar(ch,k);
  cout<<"Enter the no. of columns of matrix"<<endl;
  cin>>n;
  int *ar2= keyfunctio(n);
  int key2 = n;
  trans(ch2,key2,ar2);
}