Submission #646915

#	Time	Username	Problem	Language	Result	Execution time	Memory
646915		LeonaRaging	Exam (eJOI20_exam)	C++14	100 / 100	176 ms	100060 KiB

exam

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

#define fi first
#define se second
#define ll long long
#define pb push_back
#define db(val) "[" #val " = " << (val) << "] "

const ll mod = 1e9 + 7;
const int maxn = 1e5 + 4;
const int INF = 1e9;
const int N = 5005;

int n, a[maxn], b[maxn], L[maxn], R[maxn];
set<int> mySet;

void Sub2() {
    int res = 0, pre = 0;
    for (int i = 1; i <= n; i++)
        if (a[i] == b[i]) {
            res += R[i] - max(pre, L[i]) - 1;
            pre = R[i];
            i = R[i] - 1;
        }
    cout << res;
}

struct seg_tree {
    vector<int> t;
    seg_tree() {
        t.resize(4 * maxn);
    }
    void update(int pos, int val, int v = 1, int l = 1, int r = maxn - 1) {
        if (l == r) {
            t[v] = val;
            return;
        }
        int m = (l + r) / 2;
        if (pos <= m) update(pos, val, 2 * v, l, m);
        else update(pos, val, 2 * v + 1, m + 1, r);
        t[v] = max(t[2 * v], t[2 * v + 1]);
    }
    int get(int l, int r, int v = 1, int tl = 1, int tr = maxn - 1) {
        if (tl > r || tr < l) return 0;
        if (tl >= l && tr <= r) return t[v];
        int m = (tl + tr) / 2;
        int L = get(l, r, 2 * v, tl, m);
        int R = get(l, r, 2 * v + 1, m + 1, tr);
        return max(L, R);
    }
} IT;

map<int,int> mp;

void Sub4() {
    for (int i = 1; i <= n; i++)
        mp[a[i]] = i;
    for (int i = 1; i <= n; i++) {
        auto it = mp.find(b[i]);
        if (it == mp.end()) continue;
        int idx = it->se;
        if (L[idx] < i && R[idx] > i)
            IT.update(idx, IT.get(1, idx) + 1);
    }
    cout << IT.t[1];
}

int dp[N][N];

void Sub6() {
    int res = 0;
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= n; j++) {
            if (a[i] == b[j] && L[i] < j && j < R[i])
                dp[i][j] = dp[i][j - 1] + 1;
            dp[i][j] = max({dp[i][j], dp[i][j - 1], dp[i - 1][j]});
            res = max(res, dp[i][j]);
        }
    cout << res << '\n';
}

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    //freopen(".INP", "r", stdin);
    //freopen(".OUT", "w", stdout);
    cin >> n;
    for (int i = 1; i <= n; i++)
        cin >> a[i];
    for (int i = 1; i <= n; i++) {
        cin >> b[i];
        mySet.insert(b[i]);
    }
    stack<int> st;
    st.push(0);
    a[0] = a[n + 1] = INF + 1;
    for (int i = 1; i <= n; i++) {
        while (a[st.top()] <= a[i])
            st.pop();
        L[i] = st.top();
        st.push(i);
    }
    stack<int>().swap(st);
    st.push(n + 1);
    for (int i = n; i >= 1; i--) {
        while (a[st.top()] <= a[i])
            st.pop();
        R[i] = st.top();
        st.push(i);
    }
    if (mySet.size() == 1) Sub2();
    else if (n > 5000) Sub4();
    else { 
        Sub6();
    }
}

• Subtask 1: 14 / 14
• Subtask 2: 12 / 12
• Subtask 3: 13 / 13
• Subtask 4: 23 / 23
• Subtask 5: 16 / 16
• Subtask 6: 22 / 22