Submission #61233227

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Source Code Expand

// answer = size[0] * (-n-1)^[# other components - 1]

#include <bits/stdc++.h>
using namespace std;
const int MOD = 998244353;

int n, p[100005];
pair<int, int> dp[100005][2];
vector<int> G[100005];

int power(int x, int t) {
    int ret = 1;
    while(t > 0) {
        if(t & 1) ret = 1LL * ret * x % MOD;
        x = 1LL * x * x % MOD;
        t >>= 1;
    }
    return ret;
}

pair<int, int> operator+(const pair<int, int>& A, const pair<int, int>& B) {
    return make_pair((A.first + B.first) % MOD, (A.second + B.second) % MOD);
}
pair<int, int> operator*(const pair<int, int>& A, const pair<int, int>& B) {
    return make_pair(1LL * A.first * B.first % MOD, (1LL * A.first * B.second + 1LL * A.second * B.first) % MOD);
}

int main() {
    scanf("%d", &n);
    for(int i = 2; i <= n; i++) scanf("%d", &p[i]);

    for(int i = 2; i <= n; i++) G[p[i]].push_back(i);
    for(int i = n; i >= 1; i--) {
        dp[i][0] = make_pair(1, 1);
        dp[i][1] = make_pair(1, 0);
        for(auto ni : G[i]) {
            dp[i][0] = dp[i][0] * (dp[ni][0] * make_pair(n * 2, 0) + dp[ni][1] * make_pair(MOD - n - 1, 0));
            dp[i][1] = dp[i][1] * (dp[ni][0] * make_pair(n * 2 - 1, 0) + dp[ni][1] * make_pair(MOD - n, 0));
        }
    }
    pair<int, int> ans = dp[1][0] * make_pair(n * 2 + 1, 0) + dp[1][1] * make_pair(MOD - n - 1, 0);
    printf("%lld\n", 1LL * (ans.first + ans.second) * power(n + 1, MOD - 2) % MOD);
    return 0;
}

Submission Info

Compile Error

Main.cpp: In function ‘int main()’:
Main.cpp:29:10: warning: ignoring return value of ‘int scanf(const char*, ...)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   29 |     scanf("%d", &n);
      |     ~~~~~^~~~~~~~~~
Main.cpp:30:38: warning: ignoring return value of ‘int scanf(const char*, ...)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   30 |     for(int i = 2; i <= n; i++) scanf("%d", &p[i]);
      |                                 ~~~~~^~~~~~~~~~~~~

Judge Result