2834: 回家的路
Time Limit: 10 Sec Memory Limit: 128 MB
Submit: 62 Solved: 38
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Description
Input
Output
Sample Input
2 1
1 2
1 1 2 2
Sample Output
5
HINT
N<=20000,M<=100000
Source
dijkstra+堆优化+分层图
把所有的横向和纵向分开看。跑最短路即可。
注意：N这么大，不能写N^2建图。要把M个位置去建图。
1 #include<bits/stdc++.h>
2 using namespace std;
3 #define MAXN 20010
4 #define MAXM 100010
5 #define INF 1e9
6 struct NODE
7 {
8 int begin,end,value,next;
9 }edge[6*MAXM+10];
10 struct node
11 {
12 int x,y,id;
13 }a[MAXM+10];
14 int cnt,Head[2*MAXM+10],pos[2*MAXM+10],Heap[2*MAXM+10],dis[2*MAXM+10],N,SIZE;
15 void addedge(int bb,int ee,int vv)
16 {
17 edge[++cnt].begin=bb;edge[cnt].end=ee;edge[cnt].value=vv;edge[cnt].next=Head[bb];Head[bb]=cnt;
18 }
19 void addedge1(int bb,int ee,int vv)
20 {
21 addedge(bb,ee,vv);addedge(ee,bb,vv);
22 }
23 int read()
24 {
25 int s=0,fh=1;char ch=getchar();
26 while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)fh=-1;ch=getchar();}
27 while(ch>=‘0‘&&ch<=‘9‘){s=s*10+(ch-‘0‘);ch=getchar();}
28 return s*fh;
29 }
30 //int xy(int x,int y){return (x-1)*n+y;}
31 void Push1(int k)
32 {
33 int now=k,root;
34 while(now>1)
35 {
36 root=now/2;
37 if(dis[Heap[root]]<=dis[Heap[now]])return;
38 swap(Heap[root],Heap[now]);
39 swap(pos[Heap[root]],pos[Heap[now]]);
40 now=root;
41 }
42 }
43 void Insert(int k)
44 {
45 Heap[++SIZE]=k;pos[k]=SIZE;Push1(SIZE);
46 }
47 void Pop1(int k)
48 {
49 int now,root=k;
50 pos[Heap[k]]=0;Heap[k]=Heap[SIZE--];if(SIZE>0)pos[Heap[k]]=k;
51 while(root<=SIZE/2)
52 {
53 now=root*2;
54 if(now<SIZE&&dis[Heap[now+1]]<dis[Heap[now]])now++;
55 if(dis[Heap[root]]<=dis[Heap[now]])return;
56 swap(Heap[root],Heap[now]);
57 swap(pos[Heap[root]],pos[Heap[now]]);
58 root=now;
59 }
60 }
61 void dijkstra(int start)
62 {
63 int i,u,v;
64 for(i=1;i<=N;i++)dis[i]=INF;dis[start]=0;
65 for(i=1;i<=N;i++)Insert(i);
66 while(SIZE>0)
67 {
68 u=Heap[1];Pop1(pos[u]);
69 for(i=Head[u];i!=-1;i=edge[i].next)
70 {
71 v=edge[i].end;
72 if(dis[v]>dis[u]+edge[i].value){dis[v]=dis[u]+edge[i].value;Push1(pos[v]);}
73 }
74 }
75 }
76 bool cmp1(node aa,node bb)
77 {
78 if(aa.x==bb.x)return aa.y<bb.y;
79 return aa.x<bb.x;
80 }
81 bool cmp2(node aa,node bb)
82 {
83 if(aa.y==bb.y)return aa.x<bb.x;
84 return aa.y<bb.y;
85 }
86 int main()
87 {
88 int n,m,i,k,k1,bx,by,ex,ey;
89 n=read();m=read();
90 memset(Head,-1,sizeof(Head));cnt=1;
91 N=2*m+4;
92 for(i=1;i<=m+2;i++)a[i].x=read(),a[i].y=read(),a[i].id=i;
93 sort(a+1,a+m+3,cmp1);
94 for(i=1;i<=m+1;i++)
95 {
96 if(a[i].x==a[i+1].x)addedge1(a[i].id,a[i+1].id,2*(a[i+1].y-a[i].y));
97 }
98 sort(a+1,a+m+3,cmp2);
99 for(i=1;i<=m+1;i++)
100 {
101 if(a[i].y==a[i+1].y)addedge1(a[i].id+m+2,a[i+1].id+m+2,2*(a[i+1].x-a[i].x));
102 }
103 for(i=1;i<=m;i++)addedge1(i,i+m+2,1);
104 addedge1(m+1,m+1+m+2,0);addedge1(m+2,m+2+m+2,0);
105 dijkstra(m+1);
106 if(dis[m+2]!=INF)printf("%d",dis[m+2]);
107 else printf("-1");
108 /*不看n的范围的后果。。。写了个n^2的建图。。。
109 for(i=1;i<=m;i++)
110 {
111 x=read();y=read();
112 k=xy(x,y);
113 addedge1(k,n*n+k,1);
114 }
115 for(i=1;i<=n;i++)
116 {
117 for(j=1;j<=n;j++)
118 {
119 if(i<n){k=xy(i,j);k1=xy(i+1,j);addedge1(k,k1,2);addedge1(k+n*n,k1+n*n,2);}
120 if(j<n){k=xy(i,j);k1=xy(i,j+1);addedge1(k,k1,2);addedge1(k+n*n,k1+n*n,2);}
121 }
122 }
123 N=2*n*n;
124 bx=read();by=read();ex=read();ey=read();
125 addedge1(xy(bx,by),xy(bx,by)+n*n,0);
126 addedge1(xy(ex,ey),xy(ex,ey)+n*n,0);
127 dijkstra(xy(bx,by));
128 if(dis[xy(ex,ey)]!=INF)printf("%d",dis[xy(ex,ey)]);
129 else printf("-1");*/
130 fclose(stdin);
131 fclose(stdout);
132 return 0;
133 }
时间： 2024-10-04 13:12:03