pku 3592 Instantaneous Transference tarjan缩点重建图+spfa求最长路

http://poj.org/problem?id=3592

#include <cstdio>
#include <cstring>
#include <iostream>
#include <queue>
#define maxn 44
#define N 2002
using namespace std;

int dir[2][2] = {{0,1},{1,0}};
const int inf = 99999999;

struct node
{
    int v,w;
    int next;
}g1[N*N],g2[N*N];

int head1[N],head2[N],ct1,ct2;
int low[N],dfn[N],stack[N],val[N];
int bcnt,top,index,num[maxn][maxn],kpos[N];
int belong[N],sum[N],dis[N];
bool inq[N],ins[N];
int n,m,ct,knum,s;
char str[maxn][maxn];


void add1(int u,int v)
{
    g1[ct1].v = v;
    g1[ct1].next = head1[u];
    head1[u] = ct1++;
}
void add2(int u,int v,int w)
{
    g2[ct2].v = v;
    g2[ct2].w  =w;
    g2[ct2].next = head2[u];
    head2[u] = ct2++;
}
void tarjan(int i)
{
    int k,j;
    low[i] = dfn[i] = ++index;
    ins[i] = true;
    stack[++top] = i;
    for (k = head1[i]; k != -1; k = g1[k].next)
    {
        int j = g1[k].v;
        if (!dfn[j])
        {
            tarjan(j);
            low[i] = min(low[i],low[j]);
        }
        else if (ins[j])
        {
            low[i] = min(low[i],dfn[j]);
        }
    }
    if (dfn[i] == low[i])
    {
        bcnt++;
        do
        {
            j = stack[top--];
            ins[j] = false;
            belong[j] = bcnt;
        }while (j != i);
    }
}
void build1()
{
    int i,j,k,x,y;
    memset(num,0,sizeof(num));
    memset(kpos,0,sizeof(kpos));
    memset(val,0,sizeof(val));
    ct = knum = 0;
    scanf("%d%d",&n,&m);
    for (i = 0; i < n; ++i)
    {
        scanf("%s",str[i]);
        for (j = 0; j < m; ++j)
        {
            if (str[i][j] == '#') continue;
            num[i][j] = ++ct;
            if (str[i][j] >= '0' && str[i][j] <= '9')
            val[num[i][j]] = str[i][j] - '0';
            else
            {
                kpos[knum++] = num[i][j];//记录每个*点，应为后边依次输入其传输的坐标
                val[num[i][j]] = 0;
            }
        }
    }
    memset(head1,-1,sizeof(head1));
    ct1 = 0;
    for (i = 0; i < n; ++i)
    {
        for (j = 0; j < m; ++j)
        {
            if (str[i][j] == '#') continue;
            for (k = 0; k < 2; ++k)
            {
                int tx = i + dir[k][0];
                int ty = j + dir[k][1];
                if (tx >= 0 && tx < n && ty >= 0 && ty < m)
                add1(num[i][j],num[tx][ty]);
            }
        }
    }
     //根据*点传输的坐标添加边
    for (i = 0; i < knum; ++i)
    {
        scanf("%d%d",&x,&y);
        add1(kpos[i],num[x][y]);
    }

    memset(dfn,0,sizeof(dfn));
    memset(low,0,sizeof(low));
    memset(ins,false,sizeof(ins));
    memset(belong,0,sizeof(belong));
    top = index = bcnt = 0;
    for (i = 1; i <= ct; ++i)
    {
        if (!dfn[i]) tarjan(i);//tarjan缩点
    }
    //缩点后计算权值
    memset(sum,0,sizeof(sum));
    for (i = 1; i <= ct; ++i)
    sum[belong[i]] += val[i];
}
void build2()
{
    int i,k;
    s = 0;
    memset(head2,-1,sizeof(head2));//加入超级源点
    ct2 = 0;
    add2(s,belong[1],sum[belong[1]]);
    for (i = 1; i <= ct; ++i)
    {
        for (k = head1[i]; k != -1; k = g1[k].next)
        {
            int j = g1[k].v;
            if (belong[i] != belong[j])
            {
                add2(belong[i],belong[j],sum[belong[j]]);
            }
        }
    }
}
void spfa(int s)
{
    int i;
    queue<int>q;
    for (i = 0; i < N; ++i)
    {
        dis[i] = -inf;
        inq[i] = false;
    }
    q.push(s); dis[s] = 0;
    inq[s] = true;
    while (!q.empty())
    {
        int u = q.front(); q.pop();
        inq[u] = false;
        for (i = head2[u]; i != -1; i = g2[i].next)
        {
            int v = g2[i].v;
            if (dis[v] < dis[u] + g2[i].w)
            {
                dis[v] = dis[u] + g2[i].w;
                if (!inq[v])
                {
                    inq[v] = true;
                    q.push(v);
                }
            }
        }
    }
}
void solve()
{
    spfa(s);//求最长路
    int ans = 0;
    for (int i = 0; i <= bcnt; ++i)
    ans = max(ans,dis[i]);
    printf("%d\n",ans);
}
int main()
{
    int t;
    scanf("%d",&t);
    while (t--)
    {
        build1();//根据题意建图
        build2();//缩点后建图
        solve();//求解
    }
    return 0;
}