http://www.51nod.com/onlineJudge/questionCode.html#!problemId=1445

題意：

思路：

挺好的一道題目，如果$colormap[i][j]$為‘Y‘，那麽這條邊的代價就是前面Y出現的次數。也就是說前面必須得都破壞了這樣才能輪到這條邊，這樣一來跑一遍最短路即可。

 1 #include<iostream>
 2 #include<algorithm>
 3 #include<cstring>
 4 #include<cstdio>
 5 #include<sstream>
 6
 
 #include<vector>
 7 #include<stack>
 8 #include<queue>
 9 #include<cmath>
10 #include<map>
11 #include<set>
12 using namespace std;
13 typedef long long ll;
14 const int INF = 0x3f3f3f3f;
15 const int maxn=3000+5;
16 const int mod=1e9+7;
17 
18 int n;
19 int
 
 tot;
20 char s[55];
21 int head[55];
22 int d[55];
23 bool done[55];
24 
25 struct node
26 {
27     int v,w,next;
28 }edge[maxn];
29 
30 struct HeapNode
31 {
32     int d,u;
33     HeapNode(){}
34     HeapNode(int d, int u):d(d),u(u){}
35     bool operator < (const HeapNode& rhs) const
 

36     {
37         return d>rhs.d;
38     }
39 };
40 
41 void addEdge(int u, int v, int w)
42 {
43     edge[tot].v=v;
44     edge[tot].w=w;
45     edge[tot].next=head[u];
46     head[u]=tot++;
47 }
48 
49 void dijkstra(int s)
50 {
51     priority_queue<HeapNode> Q;
52     for(int i=0;i<n;i++)  d[i]=INF;
53     d[s]=0;
54     memset(done,0,sizeof(done));
55     Q.push(HeapNode(0,s));
56     while(!Q.empty())
57     {
58         HeapNode x=Q.top(); Q.pop();
59         int u=x.u;
60         if(done[u])  continue;
61         done[u]=true;
62         for(int i=head[u];i!=-1;i=edge[i].next)
63         {
64             int v=edge[i].v;
65             if(d[v]>d[u]+edge[i].w)
66             {
67                 d[v]=d[u]+edge[i].w;
68                 Q.push(HeapNode(d[v],v));
69             }
70         }
71     }
72 }
73 
74 int main()
75 {
76     //freopen("in.txt","r",stdin);
77     int T;
78     scanf("%d",&T);
79     while(T--)
80     {
81         tot=0;
82         memset(head,-1,sizeof(head));
83         scanf("%d",&n);
84         for(int i=0;i<n;i++)
85         {
86             int cnt=0;
87             scanf("%s",s);
88             for(int j=0;j<n;j++)
89                 if(s[j]==‘Y‘)  {addEdge(i,j,cnt);cnt++;}
90         }
91         dijkstra(0);
92         if(d[n-1]==INF)  puts("-1");
93         else printf("%d\n",d[n-1]);
94     }
95     return 0;
96 }

51nod 1445 變色DNA（最短路變形）