[BOJ] 1987 알파벳

#include < iostream>
#include < algorithm>

using namespace std;

int n,m;

bool alpha[256];
char board[20][20];

int dy[4] = {-1,0,1,0};
int dx[4] = {0,-1,0,1};

bool check(int y,int x)
{
    for(int i=0;i<256;i++){
        if(alpha[i] == true)
            return false;
    }
    return true;
}

int cnt;
int maxNum=0;
void go(int y,int x)
{
    if(check(y,x)){
        return ;
    }

    for(int dir=0; dir<4;dir++){
        int ny = y + dy[dir];
        int nx = x + dx[dir];

        if(ny<0 || nx<0 || ny>=n || nx>=m){
            continue;
        }

        if(alpha[board[ny][nx]] == true){
            alpha[board[ny][nx]] = false;
            cnt++;
            go(ny,nx);
            maxNum = max(maxNum,cnt);
            alpha[board[ny][nx]] = true;
            cnt--;
        }

    }
    return ;
}

int main()
{
    cin>>n>>m;

    for(int i=0;i<n;i++){
        for(int j=0;j<m;j++){
            cin>>board[i][j];

            alpha[board[i][j]] = true;
        }
    }

    alpha[board[0][0]] = false;

    go(0,0);

    cout<<maxNum+1;


    return 0;
}

 

https://www.acmicpc.net/problem/1987

1987번: 알파벳