Ponding Water
设每个位置的初始高度是a[i][j],最终可以达到的高度是h[i][j]。首先，对于最外圈的每个位置，a[i][j] = h[i][j]。然后将最外圈每个位置加入优先队列(高度小的元素在对首)，取一个位置t出列，遍历t的相邻位置x，如果a[x]<h[t]。那么a[x]能够达到的最大高度就是h[t]，否则h[x] = a[x]。按照这种思路bfs即可。
注意结构体的初始化。可以利用结构体的构造函数，从而减小代码量。
1: #include <iostream>
2: #include <cstdio>
3: #include <queue>
4: #include <algorithm>
5: #include <cstring>
6: using namespace std;
7: struct node{
8: int r,c,h;
9: node(){};
10: node(int xx, int yy, int hh):r(xx),c(yy),h(hh){}
11: bool operator < (const node &s) const
12: {
13: return h>s.h; // 最小值优先
14: }
15: };
16: const int maxn = 105;
17: int row,col;
18: int a[maxn][maxn],h[maxn][maxn];
19: bool vis[maxn][maxn];
20: int dx[] = {0,0,1,-1};
21: int dy[] = {1,-1,0,0};
22: priority_queue<node> q;
23: int sum;
24: int main()
25: {
26: //freopen("test.txt","r",stdin);
27: while(scanf("%d%d",&row,&col) != EOF)
28: {
29: memset(vis,0,sizeof(vis));
30: for(int i=0;i<row;++i)
31: for(int j=0;j<col;++j)
32: scanf("%d",&a[i][j]);
33: memcpy(h,a,sizeof(a));
34: for(int i=0;i<col;++i)
35: {
36: q.push(node(0,i,a[0][i]));
37: vis[0][i] = 1;
38: q.push(node(row-1,i,a[row-1][i]));
39: vis[row-1][i] = 1;
40: }
41: for(int i=1;i<row-1;++i)
42: {
43: q.push(node(i,0,a[i][0]));
44: vis[i][0] = 1;
45: q.push(node(i,col-1,a[i][col-1]));
46: vis[i][col-1] = 1;
47: }
48: int tr,tc;
49: //sum = 0;
50: while(!q.empty())
51: {
52: node temp = q.top();
53: q.pop();
54: for(int i=0;i<4;++i)
55: {
56: tr = temp.r + dx[i];
57: tc = temp.c + dy[i];
58: if(tr>0 && tr<row-1 && tc >0 && tc < col-1 && !vis[tr][tc])
59: {
60: if(a[tr][tc] < h[temp.r][temp.c])
61: h[tr][tc] = h[temp.r][temp.c];
62: /*{
63: h[tr][tc] = h[temp.r][temp.c];
64: cout<<tr<<' '<<tc<<' '<<a[tr][tc]<<"->"<<h[tr][tc]<<endl;
65: }*/
66:
67: vis[tr][tc] = 1;
68: q.push(node(tr,tc,h[tr][tc]));
69: }
70: }
71:
72: }
73: sum = 0;
74: //for(int i=0;i<row;++i)
75: //{
76: // for(int j=0;j<col;++j)
77: // cout<<a[i][j]<<' ';
78: // cout<<endl;
79: //}
80: //cout<<endl;
81: //for(int i=0;i<row;++i)
82: //{
83: // for(int j=0;j<col;++j)
84: // cout<<h[i][j]<<' ';
85: // cout<<endl;
86: //}
87: for(int i=0;i<row;++i)
88: for(int j=0;j<col;++j)
89: sum+=h[i][j] - a[i][j];
90: printf("%d\n",sum);
91:
92:
93: }
94: }
