Submission #1282902

#	Time	Username	Problem	Language	Result	Execution time	Memory
1282902		kzhi	Fancy Fence (CEOI20_fancyfence)	C++20	100 / 100	54 ms	6108 KiB

fancyfence

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

#define left(id) (id << 1)
#define right(id) ((id << 1) | 1)
#define mid(l,r) ((l + r) >> 1)

const int N = 1e5 + 5;
const int MOD = 1e9 + 7;

int n, h[N], w[N];
int l[N], r[N];
long long t[N];

struct DATA{
    int id, val;
};

bool cmp(DATA A, DATA B){
    return A.val < B.val;
}

vector<DATA> a;

int calc(long long len){
    if (len <= 0) return 0;
    __int128 x = (__int128)len;
    __int128 res = x * (x + 1) / 2;
    res %= MOD;
    return (int)res;
}

int st[N * 4];
int lz[N * 4];

long long sum(int l, int r){
    if (l > r) return 0;
    return t[r] - t[l - 1];
}

void down(int id, int l, int r){
    if (lz[id] == 0) return;
    if (l == r){
        lz[id] = 0;
        return;
    }
    int m = mid(l, r);
    int lc = left(id), rc = right(id);
    st[lc] = lz[id];
    st[rc] = lz[id];
    lz[lc] = lz[id];
    lz[rc] = lz[id];
    lz[id] = 0;
}

void upd(int id, int l, int r, int u, int v, int val){
    if (v < l || r < u) return;
    down(id, l, r);
    if (u <= l && r <= v){
        st[id] = val;
        lz[id] = val;
        return;
    }
    int m = mid(l, r);
    upd(left(id), l, m, u, v, val);
    upd(right(id), m + 1, r, u, v, val);
}

int Get(int id, int l, int r, int pos){
    if (l == r) return st[id];
    down(id, l, r);
    int m = mid(l, r);
    if (pos <= m) return Get(left(id), l, m, pos);
    else return Get(right(id), m + 1, r, pos);
}

void SOLVE(){
    cin >> n;
    for (int i = 1; i <= n; i++)
        cin >> h[i];
    for (int i = 1; i <= n; i++){
        cin >> w[i];
        t[i] = t[i - 1] + w[i];
    }

    stack<int> st1;
    st1.push(0);
    for (int i = 1; i <= n; i++){
        while (h[st1.top()] >= h[i])
            st1.pop();
        l[i] = st1.top() + 1;
        st1.push(i);
    }

    stack<int> st2;
    st2.push(n + 1);
    for (int i = n; i >= 1; i--){
        while (h[st2.top()] >= h[i])
            st2.pop();
        r[i] = st2.top() - 1;
        st2.push(i);
    }

    for (int i = 1; i <= n; i ++)
        a.push_back({i, h[i]});

    sort(a.begin(), a.end(), cmp);

    long long ans = 0;

    for (auto i : a){
        int id = i.id;
        int val = i.val;
        long long len = sum(l[id], r[id]);
        int r1 = calc(len);
        int h1 = Get(1, 1, n, id);
        int r2 = calc(h1);
        long long s = 1ll * r1 * calc(val) % MOD;
        long long f = 1ll * r2 * r1 % MOD;
        long long add = s - f;
        add %= MOD;
        if (add < 0) add += MOD;
        ans += add;
        if (ans >= MOD) ans -= MOD;
        upd(1, 1, n, l[id], r[id], val);
    }

    cout << ans;
}

signed main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);

    #define TASK "hist"
    if (fopen(TASK".inp","r")){
        freopen(TASK".inp","r",stdin);
        freopen(TASK".out","w",stdout);
    }

    int nTest = 1;

//    cin >> nTest;

    while (nTest--){
        SOLVE();
    }
    return 0;
}

Compilation message (stderr)

fancyfence.cpp: In function 'int main()':
fancyfence.cpp:137:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  137 |         freopen(TASK".inp","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
fancyfence.cpp:138:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  138 |         freopen(TASK".out","w",stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 0
• Subtask 2: 12 / 12
• Subtask 3: 13 / 13
• Subtask 4: 15 / 15
• Subtask 5: 15 / 15
• Subtask 6: 18 / 18
• Subtask 7: 27 / 27