HDU 2235

#include <iostream>
#include <cstdio>
#include <string.h>
#include <algorithm>
using namespace std;
const int maxn = 1001 ;
struct point{
  int loca,H;
  point( int a = 0 ,int c = 0 ){
    loca = a ; H = c ;
  }
  bool operator < (  const point &A ) const {
       return H < A.H||(H==A.H&&loca<A.loca) ;
  }
}hight[ maxn * maxn ];
struct node{
   int num , H ;
}map[ maxn ][ maxn ];
int per[ maxn * maxn ],n,m;
int xx[]={ 0 , 0, 1, -1 };
int yy[]={ 1 , -1, 0, 0 };
bool mark[ maxn ][ maxn ];
int F(int x){
    if( x == per[x] ) return x ;
    per[ x ] = F( per[ x ] );
    return per[ x ];
}
int main()
{

    while(scanf("%d%d",&n,&m)==2){

           for( int i = 0 ; i < n ; ++ i )
               for( int j = 0 ; j < m ; ++ j ){
                  per[ i * m + j ] = i * m + j ;
                  map[ i ][ j ].num = 1 ;
                  scanf("%d",&map[i][j].H);
                  hight[ i * m + j ]= point( i * m + j , map[ i ][ j ].H );
                  mark[ i ][ j ] = false;
               }
               __int64 ans = 0;
          sort( hight , hight + n*m );
          for( int i = 0 ; i < n*m ; ++ i ){
                bool falg = false ;
                int Tx = hight[ i ].loca/m;
                int Ty = hight[ i ].loca%m;
                mark[Tx][Ty] = true;
                for( int j = 0 ; j< 4 ; ++ j ){
                    int x = Tx + xx[ j ];
                    int y = Ty + yy[ j ];
                    if( x < 0 || y < 0 || x >= n || y >= m ){
                            falg = true;
                            continue;
                    }
                    int fa = F( x * m + y );
                    if( fa == hight[ i ].loca ) continue;
                    int fx = fa / m;
                    int fy = fa % m;
                    if( mark[ fx ][ fy ] == true && map[ fx ][ fy ].num != 0 ){
                          ans += ( map[Tx][Ty].H - map[ fx ][ fy ].H ) * map[fx][fy].num;
                          per[ fa ] = hight[ i ].loca ;
                          map[ Tx ][ Ty ].num += map[ fx ][ fy ].num;
                    } else  if( map[ fx ][ fy ].num == 0 ) {
                        falg = true ;
                        per[ fa ] = hight[ i ].loca;
                    }
                }
                if( falg ) map[ Tx ][ Ty ].num = 0;
          }
          printf("%I64d\n",ans);
    }
    return 0;
}