HRBUST 1214 方格取数

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <cmath>
 5 #include <algorithm>
 6 #include <climits>
 7 #include <vector>
 8 #include <queue>
 9 #include <cstdlib>
10 #include <string>
11 #include <set>
12 #include <stack>
13 #define LL long long
14 #define pii pair<int,int>
15 #define INF 0x3f3f3f3f
16 using namespace std;
17 const int maxn = 400;
18 struct arc{
19     int v,w,f,next;
20     arc(int x = 0,int y = 0,int z = 0,int nxt = 0){
21         v = x;
22         w = y;
23         f = z;
24         next = nxt;
25     }
26 };
27 arc e[1000];
28 int head[maxn],d[maxn],p[maxn],S,T,n,mp[15][15],tot;
29 bool in[maxn];
30 queue<int>q;
31 void add(int u,int v,int w,int f){
32     e[tot] = arc(v,w,f,head[u]);
33     head[u] = tot++;
34     e[tot] = arc(u,-w,0,head[v]);
35     head[v] = tot++;
36 }
37 bool spfa(){
38     for(int i = 0; i < maxn; i++){
39         d[i] = INF;
40         in[i] = false;
41         p[i] = -1;
42     }
43     while(!q.empty()) q.pop();
44     d[S] = 0;
45     in[S] = true;
46     q.push(S);
47     while(!q.empty()){
48         int u = q.front();
49         q.pop();
50         in[u] = false;
51         for(int i = head[u]; ~i; i = e[i].next){
52             if(e[i].f > 0 && d[e[i].v] > d[u] + e[i].w){
53                 d[e[i].v] = d[u] + e[i].w;
54                 p[e[i].v]= i;
55                 if(!in[e[i].v]){
56                     in[e[i].v] = true;
57                     q.push(e[i].v);
58                 }
59             }
60         }
61     }
62     return p[T] > -1;
63 }
64 int solve(){
65     int tmp = 0,minV;
66     while(spfa()){
67         minV = INF;
68         for(int i = p[T]; ~i; i = p[e[i^1].v])
69             minV = min(minV,e[i].f);
70         for(int i = p[T]; ~i; i = p[e[i^1].v]){
71             e[i].f -= minV;
72             e[i^1].f += minV;
73             tmp += minV*e[i].w;
74         }
75     }
76     return tmp;
77 }
78 int main() {
79     int x,y,w;
80     while(~scanf("%d",&n)){
81         memset(mp,0,sizeof(mp));
82         memset(head,-1,sizeof(head));
83         S = tot = 0;
84         T = n*n*2+1;
85         while(scanf("%d %d %d",&x,&y,&w),x||y||w) mp[x][y] = w;
86         for(int i = 1; i <= n; i++){
87             for(int j = 1; j <= n; j++){
88                 add(n*(i-1)+j,n*(i-1)+j+n*n,-mp[i][j],1);
89                 add(n*(i-1)+j,n*(i-1)+j+n*n,0,INF);
90                 if(i < n) add(n*(i-1)+j+n*n,n*i+j,0,INF);
91                 if(j < n) add(n*(i-1)+j+n*n,n*(i-1)+j+1,0,INF);
92             }
93         }
94         add(S,1,0,2);
95         add(n*n*2,T,0,2);
96         printf("%d\n",-solve());
97     }
98     return 0;
99 }