Island Transport
http://acm.hdu.edu.cn/showproblem.php?pid=4280
Time Limit: 20000/10000 MS (Java/Others) Memory Limit: 65536/65536 K (Java/Others)
Total Submission(s): 13032 Accepted Submission(s): 4097
Problem Description
In the vast waters far far away, there are many islands. People are living on the islands, and all the transport among the islands relies on the ships.
You have a transportation company there. Some routes are opened for passengers. Each route is a straight line connecting two different islands, and it is bidirectional. Within an hour, a route can transport a certain number of passengers in one direction. For safety, no two routes are cross or overlap and no routes will pass an island except the departing island and the arriving island. Each island can be treated as a point on the XY plane coordinate system. X coordinate increase from west to east, and Y coordinate increase from south to north.
The transport capacity is important to you. Suppose many passengers depart from the westernmost island and would like to arrive at the easternmost island, the maximum number of passengers arrive at the latter within every hour is the transport capacity. Please calculate it.
You have a transportation company there. Some routes are opened for passengers. Each route is a straight line connecting two different islands, and it is bidirectional. Within an hour, a route can transport a certain number of passengers in one direction. For safety, no two routes are cross or overlap and no routes will pass an island except the departing island and the arriving island. Each island can be treated as a point on the XY plane coordinate system. X coordinate increase from west to east, and Y coordinate increase from south to north.
The transport capacity is important to you. Suppose many passengers depart from the westernmost island and would like to arrive at the easternmost island, the maximum number of passengers arrive at the latter within every hour is the transport capacity. Please calculate it.
Input
The first line contains one integer T (1<=T<=20), the number of test cases.
Then T test cases follow. The first line of each test case contains two integers N and M (2<=N,M<=100000), the number of islands and the number of routes. Islands are number from 1 to N.
Then N lines follow. Each line contain two integers, the X and Y coordinate of an island. The K-th line in the N lines describes the island K. The absolute values of all the coordinates are no more than 100000.
Then M lines follow. Each line contains three integers I1, I2 (1<=I1,I2<=N) and C (1<=C<=10000) . It means there is a route connecting island I1 and island I2, and it can transport C passengers in one direction within an hour.
It is guaranteed that the routes obey the rules described above. There is only one island is westernmost and only one island is easternmost. No two islands would have the same coordinates. Each island can go to any other island by the routes.
Then T test cases follow. The first line of each test case contains two integers N and M (2<=N,M<=100000), the number of islands and the number of routes. Islands are number from 1 to N.
Then N lines follow. Each line contain two integers, the X and Y coordinate of an island. The K-th line in the N lines describes the island K. The absolute values of all the coordinates are no more than 100000.
Then M lines follow. Each line contains three integers I1, I2 (1<=I1,I2<=N) and C (1<=C<=10000) . It means there is a route connecting island I1 and island I2, and it can transport C passengers in one direction within an hour.
It is guaranteed that the routes obey the rules described above. There is only one island is westernmost and only one island is easternmost. No two islands would have the same coordinates. Each island can go to any other island by the routes.
Output
For each test case, output an integer in one line, the transport capacity.
Sample Input
2
5 7
3 3
3 0
3 1
0 0
4 5
1 3 3
2 3 4
2 4 3
1 5 6
4 5 3
1 4 4
3 4 2
6 7
-1 -1
0 1
0 2
1 0
1 1
2 3
1 2 1
2 3 6
4 5 5
5 6 3
1 4 6
2 5 5
3 6 4
Sample Output
9
6
因为是双向的，所以add函数里面要改动下
1 #include<iostream> 2 #include<cstring> 3 #include<string> 4 #include<cmath> 5 #include<cstdio> 6 #include<algorithm> 7 #include<queue> 8 #include<vector> 9 #include<set> 10 #define maxn 100005 11 #define MAXN 100005 12 #define mem(a,b) memset(a,b,sizeof(a)) 13 const int N=200005; 14 const int M=200005; 15 const int INF=0x3f3f3f3f; 16 using namespace std; 17 int n; 18 struct Edge{ 19 int v,next; 20 int cap,flow; 21 }edge[MAXN*20];//注意这里要开的够大。。不然WA在这里真的想骂人。。问题是还不报RE。。 22 int cur[MAXN],pre[MAXN],gap[MAXN],path[MAXN],dep[MAXN]; 23 int cnt=0;//实际存储总边数 24 void isap_init() 25 { 26 cnt=0; 27 memset(pre,-1,sizeof(pre)); 28 } 29 void isap_add(int u,int v,int w)//加边 30 { 31 edge[cnt].v=v; 32 edge[cnt].cap=w; 33 edge[cnt].flow=0; 34 edge[cnt].next=pre[u]; 35 pre[u]=cnt++; 36 } 37 void add(int u,int v,int w){ 38 isap_add(u,v,w); 39 isap_add(v,u,w); 40 } 41 bool bfs(int s,int t)//其实这个bfs可以融合到下面的迭代里，但是好像是时间要长 42 { 43 memset(dep,-1,sizeof(dep)); 44 memset(gap,0,sizeof(gap)); 45 gap[0]=1; 46 dep[t]=0; 47 queue<int>q; 48 while(!q.empty()) 49 q.pop(); 50 q.push(t);//从汇点开始反向建层次图 51 while(!q.empty()) 52 { 53 int u=q.front(); 54 q.pop(); 55 for(int i=pre[u];i!=-1;i=edge[i].next) 56 { 57 int v=edge[i].v; 58 if(dep[v]==-1&&edge[i^1].cap>edge[i^1].flow)//注意是从汇点反向bfs，但应该判断正向弧的余量 59 { 60 dep[v]=dep[u]+1; 61 gap[dep[v]]++; 62 q.push(v); 63 //if(v==sp)//感觉这两句优化加了一般没错，但是有的题可能会错，所以还是注释出来，到时候视情况而定 64 //break; 65 } 66 } 67 } 68 return dep[s]!=-1; 69 } 70 int isap(int s,int t) 71 { 72 if(!bfs(s,t)) 73 return 0; 74 memcpy(cur,pre,sizeof(pre)); 75 //for(int i=1;i<=n;i++) 76 //cout<<"cur "<<cur[i]<<endl; 77 int u=s; 78 path[u]=-1; 79 int ans=0; 80 while(dep[s]<n)//迭代寻找增广路,n为节点数 81 { 82 if(u==t) 83 { 84 int f=INF; 85 for(int i=path[u];i!=-1;i=path[edge[i^1].v])//修改找到的增广路 86 f=min(f,edge[i].cap-edge[i].flow); 87 for(int i=path[u];i!=-1;i=path[edge[i^1].v]) 88 { 89 edge[i].flow+=f; 90 edge[i^1].flow-=f; 91 } 92 ans+=f; 93 u=s; 94 continue; 95 } 96 bool flag=false; 97 int v; 98 for(int i=cur[u];i!=-1;i=edge[i].next) 99 { 100 v=edge[i].v; 101 if(dep[v]+1==dep[u]&&edge[i].cap-edge[i].flow) 102 { 103 cur[u]=path[v]=i;//当前弧优化 104 flag=true; 105 break; 106 } 107 } 108 if(flag) 109 { 110 u=v; 111 continue; 112 } 113 int x=n; 114 if(!(--gap[dep[u]]))return ans;//gap优化 115 for(int i=pre[u];i!=-1;i=edge[i].next) 116 { 117 if(edge[i].cap-edge[i].flow&&dep[edge[i].v]<x) 118 { 119 x=dep[edge[i].v]; 120 cur[u]=i;//常数优化 121 } 122 } 123 dep[u]=x+1; 124 gap[dep[u]]++; 125 if(u!=s)//当前点没有增广路则后退一个点 126 u=edge[path[u]^1].v; 127 } 128 return ans; 129 } 130 131 struct Point{ 132 int x,y; 133 }p[maxn]; 134 135 int main(){ 136 std::ios::sync_with_stdio(false); 137 int m,s,t; 138 int T; 139 cin>>T; 140 while(T--){ 141 cin>>n>>m; 142 for(int i=1;i<=n;i++) cin>>p[i].x>>p[i].y; 143 int a,b,c; 144 isap_init(); 145 for(int i=1;i<=m;i++){ 146 cin>>a>>b>>c; 147 add(a,b,c); 148 } 149 Point tmp=p[1]; 150 s=1; 151 for(int i=1;i<=n;i++){ 152 if(tmp.x>p[i].x){ 153 tmp=p[i]; 154 s=i; 155 } 156 } 157 tmp=p[1]; 158 t=1; 159 for(int i=1;i<=n;i++){ 160 if(tmp.x<p[i].x){ 161 tmp=p[i]; 162 t=i; 163 } 164 } 165 cout<<isap(s,t)<<endl; 166 } 167 }