Submission #1269559

#	Time	Username	Problem	Language	Result	Execution time	Memory
1269559		herominhsteve	Power Plant (JOI20_power)	C++20	100 / 100	129 ms	29544 KiB

power

#include <bits/stdc++.h>
#define el '\n'
#define FNAME "NAME"
#define allof(x) x.begin(),x.end()
#define allof1(x) x.begin()+1,x.end()
#define mset(x,n) memset(x,(n),sizeof(x))
using namespace std;
const long long MOD = (long long) 1e9+7;
template<class X,class Y> bool minimize(X &a,Y b){ if (a>b) {a=b; return true;} return false;}
template<class X,class Y> bool maximize(X &a,Y b){ if (a<b) {a=b; return true;} return false;}

void setup(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);cout.tie(0);
	if (fopen(FNAME".inp","r")){
		freopen(FNAME".inp","r",stdin);
		freopen(FNAME".out","w",stdout);
	}
}

const int MAXN = 2e5 + 5;

int n;
vector<int> graph[MAXN];
vector<int> hasPower;

void init(){
	cin>>n;
	hasPower.assign(n+1,0);
	for (int i=1;i<n;i++){
		int u,v;
		cin>>u>>v;
		graph[u].push_back(v);
		graph[v].push_back(u);
	}
	string str;
	cin>>str;
	for (int i=0;i<(int)str.size();i++) hasPower[i+1] = (str[i]=='1' ? 1 : 0);
}

// ? dp[u] maximum profit at node u
vector<int> dp;
int res;

void dfs(int u,int pre){
	int curMax=0;
	int curSum=0;
	for (int v : graph[u]){
		if (v^pre){
			dfs(v,u);
			maximize(curMax,dp[v]);
			curSum+=dp[v];
		}
	}
	if (hasPower[u]){
		/*
		 * curMax + 1 = take the maximum path to its children + itself -> cannot be broken
		 * curSum - 1 = take all the children path - the repair fee of itself -> can be broken
		*/
		int opt = max(curMax+1,curSum-1);
		maximize(res,opt);
	} else{
		maximize(res,curSum);
	}
	dp[u] = max(hasPower[u], curSum - hasPower[u]);
}

void sol(){
	dp.assign(n+1,0);
	dfs(1,1);
	cout<<res;
}

int main(){
    setup();
    init();
    sol();
}

Compilation message (stderr)

power.cpp: In function 'void setup()':
power.cpp:16:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   16 |                 freopen(FNAME".inp","r",stdin);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
power.cpp:17:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   17 |                 freopen(FNAME".out","w",stdout);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

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