标签：des style blog class c code
大神博客：
给出 n 条边，m 个点，端点及边的最大流量， 求最大流
1.EK模板 时间复杂度 O(VE2)
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// CHEATBEATER 2014.5.20#include <stdio.h>#include <queue>#include<string.h>using
namespace std;#define arraysize 201int maxData = 0x7fffffff;int capacity[arraysize][arraysize]; //记录残留网络的容量int
flow[arraysize]; //标记从源点到当前节点实际还剩多少流量可用int
pre[arraysize]; //标记在这条路径上当前节点的前驱,同时标记该节点是否在队列中int
n,m;queue<int> myqueue;int
BFS(int
src,int
des){ int
i,j; while(!myqueue.empty()) //队列清空 myqueue.pop(); for(i=1; i<m+1; ++i) { pre[i]=-1; } pre[src]=0; flow[src]= maxData; myqueue.push(src); while(!myqueue.empty()) { int
index = myqueue.front(); myqueue.pop(); if(index == des) //找到了增广路径 break; for(i=1; i<m+1; ++i) { if(i!=src && capacity[index][i]>0 && pre[i]==-1) { pre[i] = index; //记录前驱 flow[i] = min(capacity[index][i],flow[index]); //关键：迭代的找到增量 myqueue.push(i); } } } if(pre[des]==-1) //残留图中不再存在增广路径 return
-1; else return
flow[des];}int
maxFlow(int
src,int
des){ int
increasement= 0; int
sumflow = 0; while((increasement=BFS(src,des))!=-1) { int
k = des; //利用前驱寻找路径 while(k!=src) { int
last = pre[k]; capacity[last][k] -= increasement; //改变正向边的容量 capacity[k][last] += increasement; //改变反向边的容量 k = last; } sumflow += increasement; } return
sumflow;}int
main(){ int
i,j; int
start,end,ci; while(scanf("%d%d", &n, &m) != EOF) { memset(capacity,0,sizeof(capacity)); memset(flow,0,sizeof(flow)); for(i=0; i<n; ++i) { scanf("%d%d%d", &start, &end, &ci); if(start == end) //考虑起点终点相同的情况 continue; capacity[start][end] +=ci; //此处注意可能出现多条同一起点终点的情况 } printf("%d\n", maxFlow(1, m)); } return
0;} |
2.大神写的ISAP + GAP + BFS 的非递归版本代码，网络采用邻接表 + 反向弧指针：据说很快
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//辉夜(tadvent) 2009.4.6#include<cstdio>#include<memory>#include<string.h>using
namespace std;const
int maxnode = 1024;const
int infinity = 2100000;struct
edge{ int
ver; // vertex int
cap; // capacity int
flow; // current flow in this arc edge *next; // next arc edge *rev; // reverse arc edge(){} edge(int
Vertex, int
Capacity, edge *Next) :ver(Vertex), cap(Capacity), flow(0), next(Next), rev((edge*)NULL){} void* operator new(size_t, void
*p){ return
p; }}*Net[maxnode];int
dist[maxnode]= {0}, numbs[maxnode] = {0}, src, des, n;void
rev_BFS(){ int
Q[maxnode], head = 0, tail = 0; for(int
i=1; i<=n; ++i){ dist[i] = maxnode; numbs[i] = 0; } Q[tail++] = des; dist[des] = 0; numbs[0] = 1; while(head != tail){ int
v = Q[head++]; for(edge *e = Net[v]; e; e = e->next){ if(e->rev->cap == 0 || dist[e->ver] < maxnode)continue; dist[e->ver] = dist[v] + 1; ++numbs[dist[e->ver]]; Q[tail++] = e->ver; } }}int
maxflow(){ int
u, totalflow = 0; edge *CurEdge[maxnode], *revpath[maxnode]; for(int
i=1; i<=n; ++i)CurEdge[i] = Net[i]; u = src; while(dist[src] < n){ if(u == des){ // find an augmenting path int
augflow = infinity; for(int
i = src; i != des; i = CurEdge[i]->ver) augflow = min(augflow, CurEdge[i]->cap); for(int
i = src; i != des; i = CurEdge[i]->ver){ CurEdge[i]->cap -= augflow; CurEdge[i]->rev->cap += augflow; CurEdge[i]->flow += augflow; CurEdge[i]->rev->flow -= augflow; } totalflow += augflow; u = src; } edge *e; for(e = CurEdge[u]; e; e = e->next) if(e->cap > 0 && dist[u] == dist[e->ver] + 1)break; if(e){ // find an admissible arc, then Advance CurEdge[u] = e; revpath[e->ver] = e->rev; u = e->ver; } else
{ // no admissible arc, then relabel this vertex if(0 == (--numbs[dist[u]]))break; // GAP cut, Important! CurEdge[u] = Net[u]; int
mindist = n; for(edge *te = Net[u]; te; te = te->next) if(te->cap > 0)mindist = min(mindist, dist[te->ver]); dist[u] = mindist + 1; ++numbs[dist[u]]; if(u != src) u = revpath[u]->ver; // Backtrack } } return
totalflow;}int
main(){ int
m, u, v, w; while(scanf("%d%d", &m, &n) != EOF){ memset(Net, 0, sizeof(Net)); memset(dist, 0, sizeof(dist)); memset(numbs, 0, sizeof(numbs)); edge *buffer = new
edge[2*m]; edge *data = buffer; src = 1; des = n; while(m--){ scanf("%d%d%d", &u, &v, &w); if
(u == v) continue; Net[u] = new((void*) data++) edge(v, w, Net[u]); Net[v] = new((void*) data++) edge(u, 0, Net[v]); Net[u]->rev = Net[v]; Net[v]->rev = Net[u]; } rev_BFS(); printf("%d\n", maxflow()); delete
[] buffer; } return
0;} |
标签：des style blog class c code
原文地址：http://www.cnblogs.com/gyf123/p/3737902.html
