Submission #725742

#	Time	Username	Problem	Language	Result	Execution time	Memory
725742		josanneo22	Alternating Heights (CCO22_day1problem1)	C++17	7 / 25	1075 ms	6956 KiB

Main

#include<bits/stdc++.h>
using namespace std;
#define int long long
inline int rd(){
	int x=0,w=1;
	char ch=getchar();
	for(;ch>'9'||ch<'0';ch=getchar()) if(ch=='-') w=-1;
	for(;ch>='0'&&ch<='9';ch=getchar()) x=x*10+ch-'0';
	return x*w;
}
const int maxn = 2e5 + 4;
int n;
vector<int> adj[maxn];
vector<char> color;
vector<int> parent;
int cycle_start, cycle_end;

bool dfs(int v) {
    color[v] = 1;
    for (int u : adj[v]) {
        if (color[u] == 0) {
            parent[u] = v;
            if (dfs(u))
                return true;
        }
        else if (color[u] == 1) {
            cycle_end = v;
            cycle_start = u;
            return true;
        }
    }
    color[v] = 2;
    return false;
}

vector<int> find_cycle() {
    color.assign(n, 0);
    parent.assign(n, -1);
    cycle_start = -1;
    for (int v = 0; v < n; v++) {
        if (color[v] == 0 && dfs(v))
            break;
    }
    if (cycle_start == -1) {
        return { -1 };
    }
    else {
        vector<int> cycle;
        cycle.push_back(cycle_start);
        for (int v = cycle_end; v != cycle_start; v = parent[v])
            cycle.push_back(v);
        cycle.push_back(cycle_start);
        reverse(cycle.begin(), cycle.end());
        return cycle;
    }
}
void solve(){
	int k,q; cin>>n>>k>>q;
	vector<int> a(n);
	for(auto&x:a) cin>>x;
	for(int queries=0;queries<q;queries++){
		int l,r; cin>>l>>r;
		l--;r--;
		for(int i=0;i<n;i++) adj[i].clear();
        int cnt=0;
		for(int i=l;i<=r;i++){
			if(cnt%2==1){
				if(i-1>=l)adj[a[i-1]].push_back(a[i]);
				if(i+1<=r) adj[a[i+1]].push_back(a[i]);
			}
			else{
				if(i+1<=r) adj[a[i]].push_back(a[i+1]);
				if(i-1>=l) adj[a[i]].push_back(a[i-1]);
			}
            cnt++;
		}
		vector<int> ok=find_cycle();
        int yeaaaa=(ok[0]==-1);
		if(yeaaaa) cout<<"YES\n";
		else cout<<"NO\n";
	}
}
signed main()
{
	ios_base::sync_with_stdio(0); cin.tie(0);
	int tt=1; //cin>>tt;
	while(tt--){
		solve();
	}
}

• Subtask 1: 0 / 4
• Subtask 2: 0 / 6
• Subtask 3: 7 / 7
• Subtask 4: 0 / 8