Ruudukko

#include <iostream>
#include <queue>
#include <vector>


using namespace std;

struct lol{
    int x;
    int y;
    int fx;
    int fy;
};

vector<lol> dp[1002][30];
int fromx[511][511];
int fromy[511][511];
int is[511][511];
int o[1013];
string m[511];

int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    int n;
    cin>>n;
    for (int i=0;i<n;i++){
        cin>>m[i];
    }
    dp[0][m[0][0]-'A'].push_back({0, 0, -1, -1});
    fromx[0][0]=-1;
    fromy[0][0]=-1;
    for (int i=0;i<n+n-1;i++){
        //cout<<i<<" "<<i<<endl;
        for (int ii=0;ii<30;ii++){
            if (dp[i][ii].size()>0){
                o[i]=ii;
                for (auto asd:dp[i][ii]){
                    //cout<<i<<" "<<asd.x<<" "<<asd.y<<" "<<(char)(ii+'A')<<endl;
                    fromx[asd.x][asd.y]=asd.fx;
                    fromy[asd.x][asd.y]=asd.fy;
                    if (asd.x<n-1&&(!is[asd.x+1][asd.y])){
                        is[asd.x+1][asd.y]=1;
                        dp[i+1][m[asd.x+1][asd.y]-'A'].push_back({asd.x+1, asd.y, asd.x, asd.y});
                    }
                    if (asd.y<n-1&&(!is[asd.x][asd.y+1])){
                        is[asd.x][asd.y+1]=1;
                        dp[i+1][m[asd.x][asd.y+1]-'A'].push_back({asd.x, asd.y+1, asd.x, asd.y});
                    }
                }
                break;
            }
        }
    }
    vector<char> vs;
    int x=n-1;
    int y=n-1;
    while (x>-1){
        vs.push_back(m[x][y]);
        int nx=fromx[x][y];
        int ny=fromy[x][y];
        if (x==nx&&y==ny) cout<<"error"<<endl;
        x=nx;
        y=ny;
    }
    for (int i=(int)vs.size()-1;i>=0;i--){
        cout<<vs[i];
    }
    cout<<endl;
}

Test 1

Group: 1

Verdict: ACCEPTED

Test 2

Group: 1

Verdict: ACCEPTED

Test 3

Group: 1

Verdict: ACCEPTED

Test 4

Group: 1

Verdict: ACCEPTED

Test 5

Group: 1

Verdict: ACCEPTED

Test 6

Group: 2

Verdict: ACCEPTED

Test 7

Group: 2

Verdict: ACCEPTED

Test 8

Group: 2

Verdict: ACCEPTED

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 2

Verdict: ACCEPTED

Test 11

Group: 3

Verdict: ACCEPTED

Test 12

Group: 3

Verdict: ACCEPTED

Test 13

Group: 3

Verdict: ACCEPTED

Test 14

Group: 3

Verdict: ACCEPTED

Test 15

Group: 3

Verdict: ACCEPTED