이런 오류가 뜨네.

소스는 아래와 같아. 오류 좀 잡아줘 횽들.

 

#include <iostream>
using namespace std;

int find(char letter){
 char arr[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'};
 int i;
 for(i=0; i<26; i++){
  if(letter=arr[i]) return i;
 }
}

char change(int a, int b){
 char arr[64]={'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','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','0','1','2','3','4','5','6','7','8','9','+','/'};
 if(a==0){
  //앞에 대문자 시전하신다는 것
  return arr[b];
 }
 else{
  int x=(10*a)+b;
  return arr[x];
 }
}

int main(){
 char str[257];
 gets_s(str); //ctrl+v해서 복사때려준다
 int i, arr[256];
 for(i=0; i<256; i++){
  arr[i]=find(str[i]);
 }
 char result[128]; //256은 '짝수'다 :)
 for(i=0; i<255; i+=2){
  //i+2 는 후행처리인가?
  result[i]=change(arr[i],arr[i+1]);
 }
 cout << result;
 return 0;
}