【网络流】 HDU 4183 Pahom on Water 拆点
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题意:求两条路 能从 400.0 -> 789.0 且这两条路不想交(除了端点400,789 )
求只能走一次的网络流需要用到拆点,
将点i 拆成 i 和 i+n i->i+n的容量为经过的次数 (这题为1 )
若i 能到达 j 则连接 i+n-> j
#include <cstdio>#include <cstring>#include <cstdlib>#include <string>#include <iostream>#include <algorithm>#include <sstream>#include <cmath>using namespace std;#include <queue>#include <stack>#include <vector>#include <deque>#include <set>#include <map>#include <time.h>;#define cler(arr, val) memset(arr, val, sizeof(arr))#define FOR(i,a,b) for(int i=a;i<=b;i++)#define IN freopen ("in.txt" , "r" , stdin);#define OUT freopen ("out.txt" , "w" , stdout);typedef long long LL;const int MAXN = 514;const int MAXM = 40101;const int INF = 0x3f3f3f3f;const int mod = 1000000007;struct Edge{ int to,next,cap,flow;} edge[MAXM]; //注意是MAXMint tol;int head[MAXN];int gap[MAXN],dep[MAXN],cur[MAXN];void init(){ tol = 0; memset(head,-1,sizeof (head));}void addedge (int u,int v,int w,int rw = 0){ edge[tol].to = v; edge[tol].cap = w; edge[tol].flow = 0; edge[tol].next = head[u]; head[u] = tol++; edge[tol].to = u; edge[tol].cap = rw; edge[tol].flow = 0; edge[tol].next = head[v]; head[v] = tol++;}int Q[MAXN];void BFS(int start,int end){ memset(dep,-1,sizeof(dep)); memset(gap,0,sizeof(gap)); gap[0] = 1; int front = 0, rear = 0; dep[end] = 0; Q[rear++] = end; while(front != rear) { int u = Q[front++]; for(int i = head[u]; i != -1; i = edge[i].next) { int v = edge[i]. to; if(dep[v] != -1)continue; Q[rear++] = v; dep[v] = dep[u] + 1; gap[dep[v]]++; } }}int S[MAXN];int sap(int start,int end, int N){ BFS(start,end); memcpy(cur,head,sizeof(head)); int top = 0; int u = start; int ans = 0; int i; while(dep[start] < N) { if(u == end) { int Min = INF; int inser; for( i = 0; i < top; i++) { if(Min > edge[S[i]].cap - edge[S[i]].flow) { Min = edge[S[i]].cap - edge[S[i]].flow; inser = i; } } for( i = 0; i < top; i++) { edge[S[i]]. flow += Min; edge[S[i]^1].flow -= Min; } ans += Min; top = inser; u = edge[S[top]^1].to; continue; } bool flag = false; int v; for( i = cur[u]; i != -1; i = edge[i]. next) { v = edge[i]. to; if(edge[i].cap - edge[i].flow && dep[v]+1 == dep[u]) { flag = true; cur[u] = i; break; } } if(flag) { S[top++] = cur[u]; u = v; continue; } int Min = N; for( i = head[u]; i != -1; i = edge[i].next) { if(edge[i].cap - edge[i].flow && dep[edge[i].to] < Min) { Min = dep[edge[i].to]; cur[u] = i; } } gap[dep[u]]--; if(!gap[dep[u]]) return ans; dep[u] = Min + 1; gap[dep[u]]++; if(u != start)u = edge[S[--top]^1].to; } return ans;}double gao(double x,double y,double a,double b){ return sqrt((x-a)*(x-a)+(y-b)*(y-b));}struct point{ double f,x,y,r; point(){};}a[202];bool cmp(point a,point b){ return a.f<b.f;}int main(){#ifndef ONLINE_JUDGE freopen("in.txt", "r", stdin);#endif int t,n; scanf("%d",&t); while(t--) { init(); scanf("%d",&n); for(int i=0;i<n;i++) scanf("%lf%lf%lf%lf",&a[i].f,&a[i].x,&a[i].y,&a[i].r); sort(a,a+n,cmp); addedge(0,n,1); addedge(n-1,2*n-1,1); for(int i=0;i<n;i++) { addedge(i,i+n,1); for(int j=i+1;j<n;j++) { if(a[i].f<a[j].f&&gao(a[i].x,a[i].y,a[j].x,a[j].y)<(a[i].r+a[j].r)) addedge(i+n,j,1); } } if(sap(0,2*n-1,2*n)==2) puts("Game is VALID"); else puts("Game is NOT VALID"); } return 0;}
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