poj3160(Tarjan+Spfa)

方法RT，但是一直wa不知道为何，感觉自己的代码写搓了

今天起来研究了一下，发现错误好多，机智的找到错误，ac

感觉好多人的题解都是dp，我觉得没那么麻烦

首先联通缩点，然后设置一个超级源点，于是只要从超级源点出发找，找到一条离超级源点最长的路径即可（缩点之后的图边是有向边），Spfa变形一下

/** this code is made by LinMeiChen* Problem:* Type of Problem:* Thinking:* Feeling:*/#include<iostream>#include<algorithm>#include<stdlib.h>#include<string.h>#include<stdio.h>#include<math.h>#include<string>#include<vector>#include<queue>#include<list>using namespace std;typedef long long lld;typedef unsigned int ud;#define oo 0x3f3f3f3f#define maxn 30003#define maxm 150015struct Edge{int v, next;}E[maxm],E2[maxm];int n, tol, num, top, tol2, g_cnt;int head[maxn], stack[maxn];int low[maxn], dfn[maxn];int dis[maxn], mark[maxn];int id[maxn], q[maxn];int front, rear;int value[maxn], va[maxn];int h[maxn];void Init(){memset(value, 0, sizeof value);memset(mark, 0, sizeof mark);memset(head, -1, sizeof head);memset(low, 0, sizeof low);memset(dfn, 0, sizeof dfn);memset(id, 0, sizeof id);memset(h, -1, sizeof h);tol = tol2 = num = top = g_cnt = 0;}void add_edge(int u, int v){E[tol].v = v;E[tol].next = head[u];head[u] = tol++;}void add_edge2(int u, int v){E2[tol2].v = v;E2[tol2].next = h[u];h[u] = tol2++;}void Tarjan(int u){dfn[u] = low[u] = ++g_cnt;stack[top++] = u;mark[u] = 1;for (int i = head[u]; i!=-1; i = E[i].next){int v = E[i].v;if (!dfn[v]){Tarjan(v);low[u] = min(low[u], low[v]);}else if (mark[v]){low[u] = min(low[u], dfn[v]);}}if (low[u] == dfn[u]){int v;num++;do{v = stack[--top];mark[v] = 0;id[v] = num;} while (v != u);}}void Reach(int s){for (int i = 0; i < n;i++)if (!dfn[i])Tarjan(i);int u, v;for (int i = 0; i < n; i++){u = i;for (int j = head[u]; j != -1; j = E[j].next){int v = E[j].v;if (id[u] != id[v])add_edge2(id[u], id[v]);}}for (int i = 1; i <= num; i++)add_edge2(s, i);for (int i = 0; i < n; i++){if (va[i]>0)value[id[i]] += va[i];}}void Spfa(int s){for (int i = 0; i <= num; i++){mark[i] = 0;dis[i] = 0;}front = rear = 0;q[rear++] = s;mark[s] = 1;dis[s] = 0;while (front < rear){int u = q[front++];mark[u] = 0;for (int i = h[u]; i != -1; i = E2[i].next){int v = E2[i].v;if (dis[u] + value[v] > dis[v]){dis[v] = dis[u] + value[v];if (!mark[v]){q[rear++] = v;mark[v] = 1;}}}}}int main(){int m, u, v;while (scanf("%d%d", &n, &m) != EOF){Init();for (int i = 0; i < n; i++)scanf("%d", &va[i]);for (int i = 1; i <= m; i++){scanf("%d%d", &u, &v);add_edge(u, v);}Reach(n + 2);Spfa(n + 2);int Max = 0;for (int i = 1; i <= num; i++){Max = max(Max, dis[i]);}printf("%d\n", Max);}return 0;}/*4 31421550 11 03 2*/