Submission #549339

#	Time	Username	Problem	Language	Result	Execution time	Memory
549339		Lobo	Railway Trip (JOI17_railway_trip)	C++17	20 / 100	2081 ms	5668 KiB

railway_trip

#include<bits/stdc++.h>
using namespace std;

const long long inf = (long long) 1e18 + 10;
const int inf1 = (int) 1e9 + 10;
#define int long long
#define dbl long double
#define endl '\n'
#define sc second
#define fr first
#define mp make_pair
#define pb push_back
#define all(x) x.begin(), x.end()

const int maxn = 1e5+10;

int n, q, k, d1[maxn], d2[maxn], a[maxn], nxl[maxn], nxr[maxn];

void shp1(int S) {
    for(int i = 1; i <= n; i++) {
        d1[i] = inf;
    }
    d1[S] = 0;
    queue<int> q; q.push(S);

    while(q.size()) {
        int v = q.front();
        q.pop();

        if(nxl[v] != 0 && d1[nxl[v]] == inf) {
            d1[nxl[v]] = d1[v]+1;
            q.push(nxl[v]);
        }
        if(nxr[v] != 0 && d1[nxr[v]] == inf) {
            d1[nxr[v]] = d1[v]+1;
            q.push(nxr[v]);
        }
    }
}
void shp2(int S) {
    for(int i = 1; i <= n; i++) {
        d2[i] = inf;
    }
    d2[S] = 0;
    queue<int> q; q.push(S);

    while(q.size()) {
        int v = q.front();
        q.pop();

        if(nxl[v] != 0 && d2[nxl[v]] == inf) {
            d2[nxl[v]] = d2[v]+1;
            q.push(nxl[v]);
        }
        if(nxr[v] != 0 && d2[nxr[v]] == inf) {
            d2[nxr[v]] = d2[v]+1;
            q.push(nxr[v]);
        }
    }
}

void solve() {
    cin >> n >> k >> q;

    for(int i = 1; i <= n; i++) {
        cin >> a[i];
    }

    //find nxl
    stack<pair<int,int>> st;
    for(int i = 1; i <= n; i++) {
        while(st.size() && st.top().fr < a[i]) {
            st.pop();
        }

        if(st.size() != 0) {
            nxl[i] = st.top().sc;
        }
        st.push(mp(a[i],i));
    }
    while(st.size()) st.pop();
    for(int i = n; i >= 1; i--) {
        while(st.size() && st.top().fr < a[i]) {
            st.pop();
        }

        if(st.size() != 0) {
            nxr[i] = st.top().sc;
        }
        st.push(mp(a[i],i));
    }

    while(q--) {
        int u,v; cin >> u >> v;
        shp1(u);
        shp2(v);
        int ans = inf;
        for(int i = 1; i <= n; i++) {
            ans = min(ans, d1[i]+d2[i]-1);
        }
        cout << ans << endl;
    }

}

int32_t main() {
    ios::sync_with_stdio(false); cin.tie(0);

    // freopen("in.in", "r", stdin);
    // freopen("out.out", "w", stdout);
    
    int tt = 1;
    // cin >> tt;
    while(tt--) {
        solve();
    }

}

• Subtask 1: 5 / 5
• Subtask 2: 15 / 15
• Subtask 3: 0 / 25
• Subtask 4: 0 / 55