HDU ACM 1532 Drainage ditches-> Network max flow template problem (EK algorithm practice)

Analysis: The maximum flow of the entry problem, BFS looking for augmented road, found to update traffic until the augmentation path can not be found.

#include <iostream> #include <queue>using namespace std; #define N 202#define MAX 0x7fffffff;class max_flow_ Ek{public:max_flow_ek () {}~max_flow_ek () {}int Run (int n,int m);p rivate:void Init (); void Read (int n); int maxflow (int s,   int d,int m); int Bfs (int s,int d,int m); int m_icap[n][n];     Record the flow of residual network int m_iflow[n];      The current traffic from the source point to the current node is available in int m_ipre[n]; The precursor of the node in the augmented path queue<int> m_q;}; int max_flow_ek::run (int n,int m) {Init (); Read (n); return Maxflow (1,m,m);}  int max_flow_ek::bfs (int s,int d,int m) {int i,index;while (!m_q.empty ()) M_q.pop (); Empty queue for (i=0;i<=m;i++)//Initialize precursor M_ipre[i]=-1;m_ipre[s]=0;m_iflow[s]=max;m_q.push (s); while (!m_q.empty ()) {in  Dex=m_q.front (); Take out the team head node M_q.pop (); if (Index==d)//Find the Grace Road Break;for (i=1;i<=m;i++) if (i!=s && m_icap[index][i]>0 && Amp M_ipre[i]==-1) {M_ipre[i]=index;m_iflow[i]=m_iflow[index]<m_icap[index][i]?m_iflow[index]:m_icap[index][i];m _q.push (i);}} if (m_ipre[d]==-1) Return-1;else return m_iflow[d];} InchT Max_flow_ek::maxflow (int s,int d,int m) {int increasement;int sumflow;int k,last;sumflow=0;while ((Increasement=Bfs (s  , d,m))!=-1) {K=d;while (k!=s) {last=m_ipre[k];m_icap[last][k]-=increasement;  Change the forward edge capacity m_icap[k][last]+=increasement; Change reverse edge capacity k=last;} Sumflow+=increasement;} return sumflow;} void Max_flow_ek::init () {memset (m_icap,0,sizeof (M_icap)); Memset (M_iflow,0,sizeof (M_iflow));} void Max_flow_ek::read (int n) {int i;int si,ei,ci;for (i=0;i<n;i++) {scanf ("%d%d%d", &si,&ei,&ci); if (Si      ==ei) continue;       The starting point may be the same as the end M_icap[si][ei]+=ci; Consider repeating input}} int main () {int n,m; Max_flow_ek Max_flow;while (scanf ("%d%d", &n,&m) ==2) {printf ("%d\n", Max_flow.    Run (N,m));}      return 0; }

HDU ACM 1532 Drainage ditches-> Network max flow template problem (EK algorithm practice)