POJ 2227 The Wedding Juicer (dfs+优先队列，传说中的floodfill)

搜索floodfill相关题目时找到的这题，题目可抽象为：一个WxH大小的方块，每个单元为一块，每个单元有一个高度，从正上方向下注水，问最多能装住多少水。

解题思路为，首先最外一圈能装的水量都是0，找出其中最低的，那么与之相邻的（最多四个）方块中，如果比他低，那必可装水至这个块的高度，同时这个装水块的高度上升为那个块的高度。如果比他高或相等，则这块不可装水。然后再找次小的，依次进行，可用优先队列priority_queue来实现，也可以手写堆。

//6935#9044110 helloworld 2227 Accepted 1640K 266MS G++ 2107B 2011-07-31 14:57:52
//9044094 NKHelloWorld 2227 Accepted 1036K 313MS C++ 2062B 2011-07-31 14:56:33
//1A
#include <cstdio>
#include <queue>
using namespace std;
typedef struct
{
    int row,col,height;
}NODE;
struct shorter
{
    bool operator()(const NODE n1,const NODE n2)
    {
        return n1.height > n2.height;
    }
};
int move[4][2] =
{
    -1,0,1,0,0,-1,0,1
};
bool visited[310][310];
int totrow,totcol,map[310][310];
priority_queue<NODE,vector<NODE>,shorter> que;
int main()
{
    int i,j,k,row,col;
    NODE now;
    scanf("%d%d",&totcol,&totrow);
    for(i=1;i<=totrow;i++)
        for(j=1;j<=totcol;j++)
            scanf("%d",&map[i][j]);
    for(i=1;i<=totrow;i++)
    {
        now.row = i;    now.col = 1;    now.height = map[i][1];
        visited[now.row][now.col] = true;
        que.push(now);
        now.col = totcol;   now.height = map[i][totcol];
        visited[now.row][now.col] = true;
        que.push(now);
    }
    for(j=2;j<=totcol-1;j++)
    {
        now.row = 1;    now.col = j;    now.height = map[1][j];
        visited[now.row][now.col] = true;
        que.push(now);
        now.row = totrow;   now.height = map[totrow][j];
        visited[now.row][now.col] = true;
        que.push(now);
    }
    int ans = 0;
    while(!que.empty())
    {
        for(i=0;i<4;i++)
        {
            now.row = que.top().row;
            now.col = que.top().col;
            now.row += move[i][0];
            now.col += move[i][1];
            if(!visited[now.row][now.col] && now.row >=1 && now.row <=totrow && now.col >=1 && now.col <= totcol)
            {
                visited[now.row][now.col] = true;
                if(map[now.row][now.col] < que.top().height)
                {
                    ans += que.top().height - map[now.row][now.col];
                    now.height = que.top().height;
                }
                else
                {
                    now.height = map[now.row][now.col];
                }
                que.push(now);
            }
        }
        que.pop();
    }
    printf("%d\n",ans);
    return 0;
}