Submission #293407

#	Time	Username	Problem	Language	Result	Execution time	Memory
293407		jainbot27	Power Plant (JOI20_power)	C++17	100 / 100	191 ms	26744 KiB

power

#pragma GCC optimize("Ofast")
#pragma GCC target("sse4,avx,avx2,fma")
#include <bits/stdc++.h>
using namespace std;


#define f first
#define s second
#define pb push_back
#define mp make_pair
#define ts to_string
#define ub upper_bound
#define lb lower_bound
#define ar array
#define all(x) x.begin(), x.end()
#define siz(x) (int)x.size()
#define FOR(x, y, z) for(int x = (y); x < (z); x++)
#define ROF(x, y, z) for(int x = (y-1); x >= (z); x--)
#define F0R(x, z) FOR(x, 0, z)
#define R0F(x, z) ROF(x, z, 0)
#define trav(x, y) for(auto&x:y)

const string nl = "\n";
using ll = int64_t;
using vi = vector<int>;
using vl = vector<ll>;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using str = string;
using vpii = vector<pii>;
using vpll = vector<pll>;


template<class T> inline bool ckmin(T&a, T b) {return b < a ? a = b, 1 : 0;}
template<class T> inline bool ckmax(T&a, T b) {return b > a ? a = b, 1 : 0;}
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
void usaco(string x=""){
    ios_base::sync_with_stdio(0); cin.tie(0); x=x;
#ifndef D
    if(siz(x)){
        freopen((x+".in").c_str(), "r", stdin);
        freopen((x+".out").c_str(), "w", stdout);
    }
#endif
}


str ts(char c) { return str(1,c); }
str ts(bool b) { return b ? "true" : "false"; }
str ts(const char* s) { return (str)s; }
str ts(str s) { return s; }
template<class A> str ts(complex<A> c) { 
    stringstream ss; ss << c; return ss.str(); }
str ts(vector<bool> v) { 
    str res = "{"; for(int i = 0;i < (int)v.size(); i++) res += char('0'+v[i]);
    res += "}"; return res; }
template<size_t SZ> str ts(bitset<SZ> b) {
    str res = ""; for(int i = 0; i < b.size(); i++) res += char('0'+b[i]);
    return res; }
template<class A, class B> str ts(pair<A,B> p);
template<class T> str ts(T v) { 
    bool fst = 1; str res = "{";
    for (const auto& x: v) {
        if (!fst) res += ", ";
        fst = 0; res += ts(x);
    }
    res += "}"; return res;
}
template<class A, class B> str ts(pair<A,B> p) {
    return "("+ts(p.f)+", "+ts(p.s)+")"; }
void DBG() { cerr << "]" << endl; }
template<class H, class... T> void DBG(H h, T... t) {
    cerr << ts(h); if (sizeof...(t)) cerr << ", ";
    DBG(t...); }


#ifdef D 
#define dbg(...) cerr << "LINE(" << __LINE__ << ") -> [" << #__VA_ARGS__ << "]: [", DBG(__VA_ARGS__)
#else
#define dbg(...) 0
#endif

const int mxN = 2e5 + 10;
int n, dp[mxN], a[mxN], ans = 0;
vi g[mxN];
void dfs(int u, int p){
    int mx = 0, sum = 0;
    trav(v, g[u]){
        if(v!=p){
            dfs(v, u);
            ckmax(mx, dp[v]); sum += dp[v];
        }
    }
    if(a[u]){
        ckmax(ans, max(mx + 1, sum - 1));
        dp[u]=max(sum-1, 1);
    }
    else{
        ckmax(ans, sum);
        dp[u]=sum;
    }
}
signed main(){
    usaco("");
    cin >> n;
    F0R(i, n-1){
        int e1, e2; cin >> e1 >> e2;
        e1--; e2--;
        g[e1].pb(e2);
        g[e2].pb(e1);
    }
    F0R(i, n){
        char x; cin >>x;
        a[i] = (x=='1');
    }
    dfs(0,-1);
    cout << ans << nl;
}
/*
 * Stuff I should try:
 * Is it Monotonic? -> Binary Search
 * Is N small? -> Bitsets or other exponential
 * Edge Cases? Look Carefully 
 * Can't figure anything out? Brute Force and see patterns
 * Try to prove greedies
 * Prefix Sums, Amortization, DP, Data Structures
*/

Compilation message (stderr)

power.cpp: In function 'void usaco(std::string)':
power.cpp:41:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   41 |         freopen((x+".in").c_str(), "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
power.cpp:42:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   42 |         freopen((x+".out").c_str(), "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 6 / 6
• Subtask 2: 41 / 41
• Subtask 3: 53 / 53