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Luogu

读优没读负数调了0.5h+，日

大概就是跑一下拓扑排序再算每个 C 就行了

注意输入层的节点不用减去其阈值

#include <iostream>
#include <cstdio>
#include <queue>

const int MaxN = 200 + 5;

int N, M, Edge, Topn;
int Indegree[MaxN], Outdegree[MaxN], FST[MaxN], U[MaxN], C[MaxN], Top[MaxN];
bool IsNull;
std::queue <int> Q;

struct Linker
{
    int to, w, nxt;
    Linker(){}
    Linker(int x, int y, int z)
    {
        to = y;
        w = z;
        nxt = FST[x];
    }
} E[MaxN * MaxN];

inline int read()
{
    register int x = 0, v = 1;
    register char ch = getchar();
    while(!isdigit(ch)) 
    {
        if(ch == '-') v = -1;
        ch = getchar();
    }
    while(isdigit(ch))
    {
        x = x * 10 + ch - '0';
        ch = getchar();
    }
    return x * v;
}

inline void AddEdge(int x, int y, int z)
{
    E[++Edge] = Linker(x, y, z);
    FST[x] = Edge;
}

int main()
{
    N = read();
    M = read();
    for(int i = 1; i <= N; ++i) 
    {
        C[i] = read();
        U[i] = read();
        if(!C[i]) C[i] -= U[i];
    }
    for(int i = 1; i <= M; ++i)
    {
        int u = read(), v = read(), w = read();
        AddEdge(u, v, w);
        ++Indegree[v];
        ++Outdegree[u];
    }
    for(int i = 1; i <= N; ++i)
    {
        if(!Indegree[i]) 
        {
            Q.push(i);
            Top[++Topn] = i;
        }
    }
    while(!Q.empty())
    {
        int from = Q.front();
        Q.pop();
        for(int k = FST[from]; k; k = E[k].nxt)
        {
            int to = E[k].to;
            if(--Indegree[to] == 0) 
            {
                Q.push(to);
                Top[++Topn] = to;
            }
        }
    }
    for(int i = 1; i <= N; ++i)
    {
        int cur = Top[i];
        if(C[cur] <= 0) continue;
        for(int k = FST[cur]; k; k = E[k].nxt)
        {
            int to = E[k].to, w = E[k].w;
            C[to] += w * C[cur];
        }
    }
    for(int i = 1; i <= N; ++i)
    {
        if(!Outdegree[i] && C[i] > 0) 
        {
            IsNull = 1;
            printf("%d %d\n", i, C[i]);
        }
    }
    if(!IsNull) 
    {
        puts("NULL");
        return 0;
    }
    return 0;
}