[백준]1620-나는야 포켓몬 마스터 이다솜(설명X, Binary search)

#include <iostream>
#include <algorithm>
#include <cstring>
using namespace std;
 
bool is_front(pair<char*, int> pair1, pair<char*, int> pair2) {
    for (size_t i = 0; i < 21; i++) {
        if (pair1.first[i] > pair2.first[i])
            return false;
        else if (pair1.first[i] < pair2.first[i])
            return true;
    }
    return true;
}
 
int main()
{
    int N, M;
    scanf("%d %d", &N, &M);
    pair<int, char*>* num_pair = new pair<int, char*>[N + 1];
    pair<char*, int>* str_pair = new pair<char*, int>[N + 1];
    for (size_t i = 1; i <= N; i++) {
        str_pair[i].first = new char[21];
        str_pair[i].second = i;
        scanf("%s", str_pair[i].first);
        num_pair[i] = { i, str_pair[i].first };
    }
    sort(str_pair + 1, str_pair + N + 1, is_front);
    for (size_t i = 0; i < M; i++) {
        char input[21] = { 0, };
        scanf("%s", &input);
        if (isdigit(input[0]))
            printf("%s\n", num_pair[(atoi(input))].second);
        else {
            int min = 1, max = N, ans = 0;
            while (max >= min) {
                int mid = (max + min) / 2;
                int diff = strcmp(input, str_pair[mid].first);
                if (diff == 0) {
                    ans = str_pair[mid].second;
                    break;
                }
                else if (diff > 0)
                    min = mid + 1;
                else
                    max = mid - 1;
            }
            printf("%d\n", ans);
        }
    }
    return 0;
}