1157번 단어공부

#include <iostream>
#include <string>
 
using namespace std;
 
int main()
{
    string s;
    cin >> s;
 
    int alpa[27] = {
        0,
    };
 
    for (int i = 0; i < s.length(); i++)
    {
        alpa[(s[i] < 'a') ? s[i] - 'A' : s[i] - 'a']++;
    }
 
    char maxChar;
    int maxIdx;
    int maxCount = 0;
 
    for (int i = 0; i < 26; i++)
    {
        if (alpa[i] > maxCount)
        {
            maxCount = alpa[i];
            maxIdx = i;
        }
    }
 
    bool isOverlap = false;
 
    for (int i = 0; i < 26; i++)
    {
        if(maxIdx == i) continue;
        if(maxCount == alpa[i]) isOverlap = true;
    }
 
    maxChar = 'A' + maxIdx;
 
    if(isOverlap) cout << "?" << "\n";
    else cout << maxChar << "\n";
}