2016 ACM/ICPC Asia Regional Qingdao Online HDU5889

链接：http://acm.hdu.edu.cn/showproblem.php?pid=5889

解法：http://blog.csdn.net/u013532224/article/details/46992973 然后改改模版

#include <iostream>
#include <cstring>
#include <cstdio>
#include <vector>
#include <queue>
#include <string.h>
using namespace std;

const int MAXN = 2200;//点数的最大值
const int MAXM = 800000;//边数的最大值
const int INF2 = 2000000000;
struct Edge1
{
    int to,next,cap,flow;
}edge[MAXM];//注意是MAXM
int tol;
int head[MAXN];
int gap[MAXN],dep[MAXN],cur[MAXN];
void init()
{
    tol = 0;
    memset(head,-1,sizeof (head));
}
void add (int u,int v,int w,int rw = 0)//网络流要有反向弧
{
    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)//有几个点
{
    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 = INF2;
            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;
}

#define typec int
typec INF=0x3f3f3f3f;//防止后面溢出，这个不能太大
bool vis[MAXN];
int pre[MAXN];
void Dijkstra(typec cost[][MAXN],typec lowcost[],int n,int beg)
{
    for(int i=0;i<n;i++)
    {
        lowcost[i]=INF;
        vis[i]=false;
        pre[i]=-1;
    }
    lowcost[beg]=0;
    for(int j=0;j<n;j++)
    {
        int k=-1;
        int Min=INF;
        for(int i=0;i<n;i++)
            if(!vis[i]&&lowcost[i]<Min)
            {
                Min=lowcost[i];
                k=i;
            }
        if(k==-1)break;
        vis[k]=true;
        for(int i=0;i<n;i++)
            if(!vis[i]&&lowcost[k]+cost[k][i]<lowcost[i])
            {
                lowcost[i]=lowcost[k]+cost[k][i];
                pre[i]=k;
            }
    }
}
int cost2[MAXN][MAXN];
int dist2[MAXN];

int cost[MAXN][MAXN];
int num[MAXN][MAXN];
int has[MAXN];
int dist[MAXN];
int main()
{
    int T;
    cin>>T;
    while(T--)
    {
    int n,m;
        scanf("%d%d",&n,&m);
    {
        init();
        memset(cost,INF,sizeof cost);
        memset(num,0,sizeof num);
        for(int i=0;i<n;i++)
            cost[i][i]=0;

        for(int i=1;i<=m;i++)//双向  有重边
        {
            int u,v,w;
            scanf("%d%d%d",&u,&v,&w);
            u--;
            v--;
            if(cost[u][v]>w)
            {
                cost[u][v]=1;
                cost[v][u]=1;
            }
            num[u][v]=w;
            num[v][u]=w;

        }
        Dijkstra(cost,dist,n,0);// wuxiangda  bulian

        memset(cost2,INF,sizeof cost2);
        for(int i=0;i<n;i++)
            cost2[i][i]=0;

        for(int i=0;i<n;i++)
        {
            for(int j=0;j<n;j++)
            {
                if(i!=j)
                    if(dist[i]-dist[j]==cost[i][j])
                    {
                        cost2[j][i]=1;
                        add(j,i,num[i][j]);
                    }
            }
        }
        Dijkstra(cost2,dist2,n,0);
        printf("%d\n",sap(0,n-1,n));
    }
    }
    return 0;
}