Submission #439073

#	Time	Username	Problem	Language	Result	Execution time	Memory
439073		meatrow	Mountains (NOI20_mountains)	C++17	100 / 100	1018 ms	31000 KiB

Mountains

#include <iostream>
#include <vector>
#include <cstring>
#include <algorithm>
#include <map>
using namespace std;
int t[1200000];
long long g[300000];
int left1[300000], right1[300000];
void update (int v, int tl, int tr, int h) {
    if (tl == tr)
        t[v]++;
    else {
        int tm = (tl + tr) / 2;
        if (h <= tm)
            update (v*2, tl, tm, h);
        else
            update (v*2+1, tm+1, tr, h);
        t[v] = t[v*2] + t[v*2+1];
    }
}
int sum (int v, int tl, int tr, int l, int r) {
    if (l > r)
        return 0;
    if (l == tl && r == tr)
        return t[v];
    int tm = (tl + tr) / 2;
    return sum (v*2, tl, tm, l, min(r,tm))
           + sum (v*2+1, tm+1, tr, max(l,tm+1), r);
}
int main(){
    int n;
    cin >> n;
    vector<long long>b;
    for(int i = 0; i < n; i++){
        cin >> g[i];
        b.push_back(g[i]);
    }
    sort(b.begin(), b.end());
    map<long long,int>c;
    for(int i = 0; i < b.size(); i++){
        c[b[i]] = i;
    }
    for(int i = 0; i < n; i++){
        g[i] = c[g[i]];
    }
    update(1, 0, n, g[0]);
    for(int i = 1; i < n - 1; i++){
        left1[i] = sum(1, 0, n, 0, g[i] - 1);
        update(1, 0, n, g[i]);
    }
    memset(t, 0, sizeof(t[0]) * 1200000);
    update(1, 0, n, g[n - 1]);
    for(int i = n - 2; i >= 1; i--){
        right1[i] = sum(1, 0, n, 0, g[i] - 1);
        update(1, 0, n, g[i]);
    }
    long long int ans = 0;
    for(int i = 1; i < n - 1; i++){
        ans += 1LL * left1[i] * right1[i];
    }
    cout << ans;
    return 0;
}

Compilation message (stderr)

Mountains.cpp: In function 'int main()':
Mountains.cpp:41:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   41 |     for(int i = 0; i < b.size(); i++){
      |                    ~~^~~~~~~~~~

• Subtask 1: 2 / 2
• Subtask 2: 4 / 4
• Subtask 3: 9 / 9
• Subtask 4: 36 / 36
• Subtask 5: 28 / 28
• Subtask 6: 9 / 9
• Subtask 7: 12 / 12