提出 #61398295

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ソースコード 拡げる

#include <bits/stdc++.h>
using namespace std;

#define int long long

vector<bool> visited; // keeps track of which vertices are already visited

// runs depth first search starting at vertex v.
// each visited vertex is appended to the output vector when dfs leaves it.
void dfs(int v, vector<vector<int>> const& adj, vector<int> &output) {
    visited[v] = true;
    for (auto u : adj[v])
        if (!visited[u])
            dfs(u, adj, output);
    output.push_back(v);
}

// input: adj -- adjacency list of G
// output: components -- the strongy connected components in G
// output: adj_cond -- adjacency list of G^SCC (by root vertices)
void strongly_connected_components(vector<vector<int>> const& adj,
                                  vector<vector<int>> &components,
                                  vector<vector<int>> &adj_cond) {
    int n = adj.size();
    components.clear(), adj_cond.clear();

    vector<int> order; // will be a sorted list of G's vertices by exit time

    visited.assign(n, false);

    // first series of depth first searches
    for (int i = 0; i < n; i++)
        if (!visited[i])
            dfs(i, adj, order);

    // create adjacency list of G^T
    vector<vector<int>> adj_rev(n);
    for (int v = 0; v < n; v++)
        for (int u : adj[v])
            adj_rev[u].push_back(v);

    visited.assign(n, false);
    reverse(order.begin(), order.end());

    vector<int> roots(n, 0); // gives the root vertex of a vertex's SCC

    // second series of depth first searches
    for (auto v : order)
        if (!visited[v]) {
            std::vector<int> component;
            dfs(v, adj_rev, component);
            components.push_back(component);
            int root = *min_element(begin(component), end(component));
            for (auto u : component)
                roots[u] = root;
        }

    // add edges to condensation graph
    adj_cond.assign(n, {});
    for (int v = 0; v < n; v++)
        for (auto u : adj[v])
            if (roots[v] != roots[u])
                adj_cond[roots[v]].push_back(roots[u]);
}

int dp[2050][2050];
vector<vector<int>> components, adj;
const int MOD = 998244353;
bool vis[2051];
int recur(int x, int val){
	if (val <= 0) return 0;
	if (dp[x][val] != -1) return dp[x][val];
	vis[x] = 1;
	int ans = 1;
	
	for (auto y : adj[x]){
		int k = recur(y, val);
		ans *= k;
		ans %= MOD;
	}
	
	ans += recur(x, val-1);
	ans %= MOD;
	
	return dp[x][val] = ans;
}

main(){
	int n, m; cin >> n >> m;
	int arr[n]; for (int x = 0; x < n; x++) cin >> arr[x];
	vector<vector<int>> adj_init(n);
	for (int x = 0; x < n; x++){
		if (x != arr[x] - 1) adj_init[arr[x] - 1].push_back(x);
	}
	strongly_connected_components(adj_init, components, adj);
	
	n = components.size();
	memset(dp, -1, sizeof(dp));
	int ans = 1;
	for (int x = 0; x < n; x++){
		if (!vis[x]){
			ans *= recur(x, m);
			ans %= MOD;
		}
	}
	
	cout << ans;
}

提出情報

コンパイルエラー

Main.cpp:88:1: warning: ISO C++ forbids declaration of ‘main’ with no type [-Wreturn-type]
   88 | main(){
      | ^~~~

ジャッジ結果