题意：

思路：

搞一个priority_queue 先把边界加进去 不断取最小的 向中间扩散

//By SiriusRen

#include <queue>

#include <cstdio>

#include <cstring>

using namespace std;

#define int long long

struct Node{int h,x,y;Node(int a,int b,int c){h=a,x=b,y=c;}};

priority_queue<Node>pq;

bool operator <(Node a,Node b){return a.h>b.h;}

int n,m,ans,a[305][305],xx[]={1,-1,0,0},yy[]={0,0,1,-1};

bool vis[305][305];

signed main(){

    memset(vis,1,sizeof(vis));

    scanf("%lld%lld",&m,&n);

    for(int i=1;i<=n;i++)for(int j=1;j<=m;j++)scanf("%lld",&a[i][j]),vis[i][j]=0;

    for(int i=1;i<=n;i++)pq.push(Node(a[i][1],i,1)),pq.push(Node(a[i][m],i,m)),vis[i][m]=vis[i][1]=1;

    for(int i=2;i<=m;i++)pq.push(Node(a[1][i],1,i)),pq.push(Node(a[n][i],n,i)),vis[n][i]=vis[1][i]=1;

    while(!pq.empty()){

        Node t=pq.top();pq.pop();

        for(int i=0;i<4;i++){

            int dx=t.x+xx[i],dy=t.y+yy[i];

            if(!vis[dx][dy]){

                if(a[dx][dy]<t.h)ans+=t.h-a[dx][dy],pq.push(Node(t.h,dx,dy));

                else pq.push(Node(a[dx][dy],dx,dy));

                vis[dx][dy]=1;

            }

        }

    }

    printf("%lld\n",ans);

}