Submission #828724

#	Time	Username	Problem	Language	Result	Execution time	Memory
828724		Alora	Valley (BOI19_valley)	C++17	100 / 100	161 ms	41924 KiB

valley

#include <bits/stdc++.h>
#define name "cownav"
#define fi(i,a,b) for(int i = a; i <= b; i++)
#define fid(i,a,b) for(int i = a; i >= b; i--)
#define ll long long
#define f first
#define se second
#define pii pair<int, int>
#define getbit(i, j) ((i >> j) & 1)
#define pb push_back
#define all(v) v.begin(), v.end()
#define maxn 100005
const int M = 1e9 + 7;
using namespace std;
int n, s, q, root, num[maxn], en[maxn], h[maxn], cha[maxn][20], cnt;
vector <pii> g[maxn];
pii a[maxn];
ll down[maxn], d[maxn], mi[maxn][20];

void dfs(int u, int fa){
    num[u] = ++cnt;
    for(auto [v, w]: g[u]) if(v != fa){
        h[v] = h[u] + 1;
        d[v] = d[u] + w;
        dfs(v, u);
        down[u] = min(down[u], down[v] + w);
    }
    en[u] = cnt;
}

void build(int u, int fa){
    for(auto [v, w]: g[u]) if(v != fa){
        cha[v][0] = u;
        mi[v][0] = down[v] - d[v];
        fi(i, 1, 19){
            cha[v][i] = cha[cha[v][i - 1]][i - 1];
            mi[v][i] = min(mi[v][i - 1], mi[cha[v][i - 1]][i - 1]);
        }
        build(v, u);
    }
}

ll get_mi(int r, int v){
    ll Mi = 1e18;
    int kc = h[r] - h[v];
    fi(i, 0, 19) if(getbit(kc, i)){
        Mi = min(Mi, mi[r][i]);
        r = cha[r][i];
    }
    Mi = min(Mi, mi[v][0]);
    return Mi;
}

bool in(int u, int v){
    return (num[u] <= num[v] && num[v] <= en[u]);
}
signed main(){
	ios_base::sync_with_stdio(0);
	cin.tie(NULL);
	//freopen(name".in","r",stdin);
	//freopen(name".out","w",stdout);
    cin >> n >> s >> q >> root;
    fi(i, 1, n - 1){
        int u, v, w;
        cin >> u >> v >> w;
        g[u].pb({v, w});
        g[v].pb({u, w});
        a[i] = {u, v};
    }
    fi(i, 1, n){
        down[i] = 1e18;
        fi(j, 0, 19) mi[i][j] = 1e18;
    }
    fi(i, 1, s){
        int x; cin >> x;
        down[x] = 0;
    }
    dfs(root, 0);
    build(root, 0);
    while(q--){
        int id, r; cin >> id >> r;
        auto [u, v] = a[id];
        if(h[v] < h[u]) swap(u, v); //assume that cha[v][0] = u;
        if(!in(v, r)){cout << "escaped" << '\n'; continue;}
        if(down[v] == 1e18) {cout << "oo" << '\n'; continue;}
        cout << d[r] + get_mi(r, v) << '\n';
    }
	return 0;
}

• Subtask 1: 9 / 9
• Subtask 2: 27 / 27
• Subtask 3: 23 / 23
• Subtask 4: 41 / 41