1 #include <iostream> 2 #include <cstdio> 3 #include <cstring> 4 using namespace std; 5 const int N = 1e5 + 5; 6 typedef long long LL; 7 struct Edge { 8     int next, to; 9 }edge[N * 10];10 LL dp[N], a[N], inf = 1e12;11 int head[N], tot, input[N];12 13 void init(int n) {14     for(int i = 1; i <= n; ++i) {15         head[i] = -1;16         dp[i] = -inf;17         input[i] = 0;18     }19     tot = 0;20 }21 22 inline void add(int u, int v) {23     edge[tot].next = head[u];24     edge[tot].to = v;25     head[u] = tot++;26 }27 28 void dfs(int u) {29     if(dp[u] != -inf)30         return ;31     for(int i = head[u]; ~i; i = edge[i].next) {32         int v = edge[i].to;33         dfs(v);34         dp[u] = max(dp[v] + a[u], dp[u]);35     }36     if(dp[u] == -inf) //若是出度为037         dp[u] = a[u];38 }39 40 int main()41 {42     int n, m;43     while(~scanf("%d %d", &n, &m)) {44         for(int i = 1; i <= n; ++i) {45             scanf("%lld", a + i);46         }47         init(n);48         int u, v;49         for(int i = 1; i <= m; ++i) {50             scanf("%d %d", &u, &v);51             add(u, v);52             input[v]++;53         }54         LL Max = -inf;55         for(int i = 1; i <= n; ++i) {56             if(!input[i]) {57                 dfs(i);58                 Max = max(Max, dp[i]);59             }60         }61         printf("%lld\n", Max);62     }63     return 0;64 }