PROG-1149: บีคุนบันคุง (2Bk)

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

const int INF = 2e9;
using pii = pair < int,pair<int,int> >;
int ar[1001][1001];
int ki[5] = {0,0,0,1,-1}, kj[5] = {0,1,-1,0,0};
int n;

int main(){

    scanf("%d",&n);
    int ar[n+1][n+1];
    long long dis[n+1][n+1];
    bool visited[n+1][n+1];
    int si=-1,sj=-1,ei=-1,ej=-1,mx=0;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=n;j++){
            dis[i][j] = INF;
            visited[i][j] = false;

            scanf("%d",&ar[i][j]);
            if(ar[i][j] == 0){
                if(si == -1&&sj == -1){
                    si = i;
                    sj = j;
                }
                else {
                    ei = i;
                    ej = j;
                }
            }
        }
    }

    priority_queue < pii , vector<pii> , greater<pii> > pq;
    dis[si][sj] = 0;
    pq.push({ 0 , {si,sj} });

    while(pq.size()>0){
        int ui,uj;
        ui = pq.top().second.first;
        uj = pq.top().second.second;
        pq.pop();

        visited[ui][uj] = true;

        if(ar[ui][uj]>mx) mx = ar[ui][uj];
        if(ui == ei && uj == ej){
            printf("%d",mx);
            break;
        }

        for(int k=1;k<=4;k++){
            if(ui+ki[k]>=1 && ui+ki[k]<=n && uj+kj[k]>=1 && uj+kj[k]<=n && visited[ui+ki[k]][uj+kj[k]]==false && dis[ui][uj]+ar[ui+ki[k]][uj+kj[k]]<dis[ui+ki[k]][uj+kj[k]] ){
                dis[ui+ki[k]][uj+kj[k]]= dis[ui][uj]+ar[ui][uj];
                pq.push({ar[ui+ki[k]][uj+kj[k]] ,{ui+ki[k],uj+kj[k]} });
            }
        }

    }



    return 0;
}