HDU 4280 Island Transport 网络流裸题
#include<stdio.h> #include<string.h> #include<iostream> #include<algorithm> #include<vector> using namespace std; #define ll int const int MAXN = 100100;//点数的最大值 const int MAXM = 400010;//边数的最大值 const int INF = 0x3f3f3f3f; struct Edge { int to,next,cap,flow; }edge[MAXM];//注意是MAXM int tol; int head[MAXN]; int gap[MAXN],dep[MAXN],cur[MAXN]; void add(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; while(dep[start] < N) { if(u == end) { int Min = INF; int inser; for(int 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(int 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(int 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(int 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; } void init(){ tol = 0; memset(head,-1,sizeof(head)); } int n, m; struct point{ int x,y; int num; bool operator<(const point&a)const{ return a.x>x; } }p[MAXN]; int main() { int i, T, j, u, v, cap;scanf("%d",&T); while(T--){ init(); scanf("%d %d",&n,&m); for(i = 1; i <= n; i++)scanf("%d %d",&p[i].x,&p[i].y), p[i].num = i; while(m--){ scanf("%d %d %d",&u,&v,&cap); add(u,v,cap); add(v,u,cap); } sort(p+1,p+1+n); printf("%d\n",sap(p[1].num, p[n].num, n)); } return 0; }