Language: C++

#include <bits/stdc++.h>
using namespace std;

int table[52][52];

bool memo[52][52][52][52];

const int leftmove = -1;
const int rightmove = 1;
const int upmove = -1;
const int downmove = 1;

int main() {

    while(1){

        int w,h;

        //scanf(" %d %d",&w,&h);

        cin >> w >> h;

        if(w==0&&h==0) break;

        int tx,ty,kx,ky;

        //scanf(" %d %d %d %d",&tx,&ty,&kx,&ky);

        cin >> tx >> ty >> kx >> ky;

        for(int i=0;i<52;i++){
            for(int j=0;j<52;j++){
                for(int k=0;k<52;k++){
                    for(int r=0;r<52;r++){
                        memo[i][j][k][r] = false;
                    }
                }
            }
        }

        for(int i=1;i<=h;i++){
            for(int j=1;j<=w;j++){
                //scanf(" %d",&table[i][j]);
                cin >> table[i][j];
            }
        }

        /*printf("\n");

        for(int i=0;i<h;i++){
            for(int j=0;j<w;j++){
                printf("%d ",table[i][j]);
            }
            printf("\n");
        }*/

        //memset(memo,false,sizeof(memo));

        queue<vector<int> > q;

        vector<int> v(5);

        v[0] = tx; v[1] = ty; v[2] = kx; v[3] = ky; v[4] = 0;

        if(table[v[0]][v[1]] == 1 || table[v[2]][v[3]] == 1){
            cout << "NA" << endl;
            continue;
        }

        if(v[0] == v[2] && v[1] == v[3]){
            check = true;
            cout << v[4] << endl;
            break;
        }

        q.push(v);

        bool check = false;

        while(!q.empty()){

            v = q.front(); q.pop();

            if(v[0] == v[2] && v[1] == v[3]){
                check = true;
                cout << v[4] << endl;
                break;
            }

            memo[v[0]][v[1]][v[2]][v[3]] = true;

            v[4]++;

            if(v[4] >= 100){
                break;
            }

            vector<int> before(5);

            for(int i=0;i<5;i++){
                before[i] = v[i];
            }

            if(v[0]+leftmove != 0 && table[v[0]+leftmove][v[1]] == 0){
                v[0]+=leftmove;
            }
            if(v[2]+rightmove != w+1 && table[v[2]+rightmove][v[3]] == 0){
                v[2]+=rightmove;
            }

            if(!memo[v[0]][v[1]][v[2]][v[3]]) {
                if(v[0] == v[2] && v[1] == v[3]){
                    check = true;
                    cout << v[4] << endl;
                    break;
                }
                memo[v[0]][v[1]][v[2]][v[3]] = true;
                q.push(v);
            }

            for(int i=0;i<5;i++){
                v[i] = before[i];
            }

            if(v[2]+leftmove != 0 && table[v[2]+leftmove][v[3]] == 0){
                v[2]+=leftmove;
            }
            if(v[0]+rightmove != w+1 && table[v[0]+rightmove][v[1]] == 0){
                v[0]+=rightmove;
            }

            if(!memo[v[0]][v[1]][v[2]][v[3]]) {
                if(v[0] == v[2] && v[1] == v[3]){
                    check = true;
                    cout << v[4] << endl;
                    break;
                }
                memo[v[0]][v[1]][v[2]][v[3]] = true;
                q.push(v);
            }


            for(int i=0;i<5;i++){
                v[i] = before[i];
            }

            if(v[3]+upmove != 0 && table[v[2]][v[3]+upmove] == 0){
                v[3]+=upmove;
            }
            if(v[1]+downmove != h+1 && table[v[0]][v[1]+downmove] == 0){
                v[1]+=downmove;
            }

            if(!memo[v[0]][v[1]][v[2]][v[3]]) {
                if(v[0] == v[2] && v[1] == v[3]){
                    check = true;
                    cout << v[4] << endl;
                    break;
                }
                memo[v[0]][v[1]][v[2]][v[3]] = true;
                q.push(v);
            }

            for(int i=0;i<5;i++){
                v[i] = before[i];
            }

            if(v[1]+upmove != 0 && table[v[0]][v[1]+upmove] == 0){
                v[1]+=upmove;
            }
            if(v[3]+downmove != h+1 && table[v[2]][v[3]+downmove] == 0){
                v[3]+=downmove;
            }

            if(!memo[v[0]][v[1]][v[2]][v[3]]) {
                if(v[0] == v[2] && v[1] == v[3]){
                    check = true;
                    cout << v[4] << endl;
                    break;
                }
                memo[v[0]][v[1]][v[2]][v[3]] = true;
                q.push(v);
            }
        }

        if(!check){
            cout << "NA" << endl;
        }



    }

    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:71:13: error: 'check' was not declared in this scope
   71 |             check = true;
      |             ^~~~~