codeforces 741D Arpa’s letter-marked tree and Mehrdad’s Dokhtar-kosh paths

題意

題解

代碼

#include<bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define rep(i, a, b) for(int i=(a); i<(b); i++)
#define sz(a) (int)a.size()
#define de(a) cout << #a << " = " << a << endl
#define dd(a) cout << #a << " = " << a << " "
#define all(a) a.begin(), a.end()
#define endl "\n"
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
//---

const int N = 505050;

int n;
int ans[N], s[N], par[N], dep[N], wson[N], sz[N], mask[22], len[1<<22];
vi g[N];
vector<pii> info[N];

inline void join(vector<pii> &a, vector<pii> &b, const int &t, const int &c, int &ans) {
    if(t) swap(a, b);
    for(auto u : b) {
        if(~len[u.fi]) ans = max(ans, len[u.fi] + u.se - c);
        rep(i, 0, 22) if(~len[u.fi ^ mask[i]]) {
            ans = max(ans, len[u.fi ^ mask[i]] + u.se - c);
        }
    }
    for(auto u : b) {
        len[u.fi] = max(len[u.fi], u.se);
    }
    a.insert(a.end(), all(b));
}

void dfs(int u, bool isw) {
    info[u].pb(mp(s[u], dep[u]));
    if(sz(g[u])) {
        for(auto v : g[u]) if(v != wson[u]) {
            dfs(v, 0);
            ans[u] = max(ans[u], ans[v]);
        }
        dfs(wson[u], 1);
        ans[u] = max(ans[u], ans[wson[u]]);
        join(info[u], info[wson[u]], 1, dep[u] * 2, ans[u]);
        for(auto v : g[u]) if(v != wson[u]) {
            join(info[u], info[v], 0, dep[u] * 2, ans[u]);
        }
        if(!isw) for(auto t : info[u]) len[t.fi] = -1;
    } else {
        if(isw) len[s[u]] = max(len[s[u]], dep[u]);
    }
}

int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(0);
    rep(i, 0, 22) mask[i] = (1 << i);
    cin >> n;
    rep(i, 2, n+1) {
        string t;
        cin >> par[i] >> t;
        int c = t[0] - ‘a‘;
        g[par[i]].pb(i);
        s[i] = s[par[i]] ^ mask[c];
        dep[i] = dep[par[i]] + 1;
    }
    for(int i = n; i; --i) {
        sz[par[i]] += ++sz[i];
        if(sz[wson[par[i]]] < sz[i]) wson[par[i]] = i;
    }
    memset(len, -1, sizeof(len));
    dfs(1, 1);
    rep(i, 1, n+1) cout << ans[i] << " ";
    cout << endl;
    return 0;
}
 

codeforces 741D Arpa’s letter-marked tree and Mehrdad’s Dokhtar-kosh paths