2Bk Greedy

#include<stdio.h>
#include<queue>
using namespace std;

struct node{
    int i,j;
    int w;
    bool operator < (const node& rhs)const
    {
        return w > rhs.w;
    }
};

bool inB(int I,int n){
    return (I >= 0 && I < n);
}

int main()
{
    int n;
    scanf("%d",&n);
    int sI,sJ;
    int arr[n][n];
    for(int i = 0 ; i < n ; i++){
        for(int j = 0 ; j < n ; j++){
            scanf("%d",&arr[i][j]);
            if(arr[i][j] == 0){
                sI = i;
                sJ = j;
            }
        }
    }
    bool visited[n][n];for(int i = 0 ; i < n ; i++)for(int j = 0 ; j < n ; j ++)visited[i][j] = false;
    priority_queue<node> pq;
    pq.push({sI,sJ,0});
    int ans = -2e9;

    int moveI[4] = {-1,0,1,0};
    int moveJ[4] = {0,1,0,-1};
    while(!pq.empty()){
        int uI = pq.top().i;
        int uJ = pq.top().j;
        int uW = pq.top().w;
        pq.pop();

        if(uW == 0 && ans != -2e9)break;
        if(visited[uI][uJ])continue;
        visited[uI][uJ] = true;

        if(uW > ans)ans = uW;
        for(int i = 0 ; i < 4 ; i++){
            int vI = uI + moveI[i];
            int vJ = uJ + moveJ[i];
            if(inB(vI,n) && inB(vJ,n) && !visited[vI][vJ]){
                pq.push({vI,vJ,arr[vI][vJ]});
            }
        }
    }
    printf("%d",ans);
    return 0;
}