Cryptography: In two arrays; how each column can guard/know the same place/position of the other while encrypting a cipher key created by a user?

Question

I am doing some basic exercises on cryptography; in one exercise I want to create two arrays, the first contains the alphabet from a to z, and for the second, I give the user the choice to form his own key alphabet. The problem I found is for example when I form the following alphabet: poiuytrezamlkjhgfdsqnbvcxw

So, I ask the user to form a sentence.. My goal is when the user forms a sentence, the letters should transform to the key alphabets he has formed. For example: The formed sentence: abyz The encrypted phrase according to your key alphabet is: poxw My problem is when I enter a sentence; the transformation always starts with the first letter of the key alphabet: "poi...". That is, the letters of the key alphabet do not exactly take the places of the original alphabet. Here is my code:

#include<stdio.h>
#include<string.h>
void main() {
    char T[26]={'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};
    char T1[26]={};
    int i;
    printf("We have the alphabet:\n");
    puts(T);
    printf("Enter your key alphabet:");
    gets(T1);
    printf("Your alphabet key is: ");
    puts(T1);
    printf("Form a phrase: ");
    gets(T);
    for(i=0;i<strlen(T);i++){
        T[i]=T1[i];
    }
    printf("The encrypted phrase according to your key alphabet is: ");
    puts(T);
}

Answer 1

Guys I found the answer after a long research. So I added another array 'userinput[]' and a variable j, I used the condition if so when I form phrase in 'userinput'[]' and this one equal 'alphabet[]'. the letters take the value of 'cipherkey[]' while guarding the positions of columns. Also I added 'for' function to i with the 'if' condition. And returned to 'j' with the 'break'.

My final code (I tried to write a clean code):

#include<stdio.h>
#include<string.h>
void main() {
    char alphabet[27]={'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z' }; 
    char cipherKey[27];  
    char userInput[27];
    printf("We have the alphabet :\n");     
    puts(alphabet); 
    printf("Enter your key alphabet: ");
    gets(cipherKey);
    printf("Your key alphabet is: ");
    printf(cipherKey);
    printf("\nForm a phrase: ");
    gets(userInput);
    int i; 
    int j; 
    for(j=0;j<strlen(userInput);j++){
        for(i=0;i<strlen(alphabet);i++){
            if(alphabet[i]==userInput[j]){
                userInput[j]=cipherKey[i];
                break;  
            }
        }
    }
    printf("The encrypted phrase according to your key alphabet is: ");
    puts(userInput);
}