poj 1949 Chores 最长路

题目链接

求出最长路.....

#include <iostream>
#include <vector>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <map>
#include <set>
#include <string>
#include <queue>
using namespace std;
#define pb(x) push_back(x)
#define ll long long
#define mk(x, y) make_pair(x, y)
#define lson l, m, rt<<1
#define mem(a) memset(a, 0, sizeof(a))
#define rson m+1, r, rt<<1|1
#define mem1(a) memset(a, -1, sizeof(a))
#define mem2(a) memset(a, 0x3f, sizeof(a))
#define rep(i, a, n) for(int i = a; i<n; i++)
#define ull unsigned long long
typedef pair<int, int> pll;
const double PI = acos(-1.0);
const double eps = 1e-8;
const int mod = 1e9+7;
const int inf = 1061109567;
const int dir[][2] = { {-1, 0}, {1, 0}, {0, -1}, {0, 1} };
const int maxn = 1e6+5;
int head[maxn], dis[10005], num, val[10005];
struct node
{
    int to, nextt, c;
}e[maxn];
void add(int u, int v, int c) {
    e[num].to = v;
    e[num].nextt = head[u];
    e[num].c = c;
    head[u] = num++;
}
void init() {
    mem1(dis);
    mem1(head);
    num = 0;
}
int dfs(int u) {
    if(~dis[u])
        return dis[u];
    int ret = val[u], ans = 0;
    for(int i = head[u]; ~i; i = e[i].nextt) {
        int v = e[i].to;
        ans = max(ans, dfs(v));
    }
    return dis[u] = ans+ret;
}
int main()
{
    int n, x, y;
    while(cin>>n) {
        init();
        for(int i = 1; i<=n; i++) {
            scanf("%d", &val[i]);
            scanf("%d", &x);
            while(x--) {
               scanf("%d", &y);
               add(y, i, val[i]);
            }
        }
        for(int i = 1; i<=n; i++) {
            if(dis[i]==-1) {
                dis[i] = dfs(i);
            }
        }
        int ans = 0;
        for(int i = 1; i<=n; i++) {
            ans = max(ans, dis[i]);
        }
        printf("%d
", ans);
    }
    return 0;
}