C. Coin Troubles 有依赖的背包 + 完全背包变形

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <assert.h>
#define IOS ios::sync_with_stdio(false)
using namespace std;
#define inf (0x3f3f3f3f)
typedef long long int LL;


#include <iostream>
#include <sstream>
#include <vector>
#include <set>
#include <map>
#include <queue>
#include <string>
#include <bitset>
const int maxn = 300 + 20;
int fa[maxn], a[maxn];
bool out[maxn];
int n, q, val;
struct node {
    int u, v, tonext;
}e[maxn * 2];
int first[maxn];
int num;
void add(int u, int v) {
    ++num;
    e[num].u = u;
    e[num].v = v;
    e[num].tonext = first[u];
    first[u] = num;
}
bool vis[maxn];
void dfs(int cur) {
    for (int i = first[cur]; i; i = e[i].tonext) {
        int v = e[i].v;
        if (vis[v]) {
            cout << 0 << endl;
            exit(0);
        }
        vis[v] = true;
        dfs(v);
        vis[v] = false;
    }
}
void calc(int cur, int ti) {
    if (cur == 0) return;
    val -= a[cur] * ti;
    if (val < 0) { //不能等于
        cout << 0 << endl;
        exit(0);
    }
    calc(fa[cur], ti + 1);
    a[cur] += a[fa[cur]];
}
int dp[100000 + 20];
const int MOD = 1e9 + 7;
void work() {
    cin >> n >> q >> val;
    for (int i = 1; i <= n; ++i) {
        cin >> a[i];
    }
    for (int i = 1; i <= q; ++i) {
        int u, v;
        cin >> u >> v;
        fa[v] = u;
        out[u] = true;
        add(u, v);
    }
    for (int i = 1; i <= n; ++i) {
//        if (vis[i]) continue;
        vis[i] = true;
        dfs(i);
        vis[i] = false;
    }
    for (int i = 1; i <= n; ++i) {
        if (out[i]) continue;
        calc(i, 0);
    }
    dp[0] = 1;
    for (int i = 1; i <= n; ++i) {
        for (int j = a[i]; j <= val; ++j) {
            dp[j] += dp[j - a[i]];
            if (dp[j] >= MOD) dp[j] %= MOD;
        }
    }
    cout << dp[val] << endl;
}

int main() {
#ifdef local
    freopen("data.txt", "r", stdin);
//    freopen("data.txt", "w", stdout);
#endif
    IOS;
    work();
    return 0;
}