Submission #829484

#	Time	Username	Problem	Language	Result	Execution time	Memory
829484		GrindMachine	Floppy (RMI20_floppy)	C++17	100 / 100	82 ms	15408 KiB

floppy

// Om Namah Shivaya

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

template<typename T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef long long int ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL)
#define pb push_back
#define endl '\n'
#define sz(a) a.size()
#define setbits(x) __builtin_popcountll(x)
#define ff first
#define ss second
#define conts continue
#define ceil2(x, y) ((x + y - 1) / (y))
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define yes cout << "Yes" << endl
#define no cout << "No" << endl

#define rep(i, n) for(int i = 0; i < n; ++i)
#define rep1(i, n) for(int i = 1; i <= n; ++i)
#define rev(i, s, e) for(int i = s; i >= e; --i)
#define trav(i, a) for(auto &i : a)

template<typename T>
void amin(T &a, T b) {
    a = min(a, b);
}

template<typename T>
void amax(T &a, T b) {
    a = max(a, b);
}

#ifdef LOCAL
#include "debug.h"
#else
#define debug(x) 42
#endif

/*

refs:
https://codeforces.com/blog/entry/112664 (cartesian trees => construction and properties)

thought process:

thought cartesian tree can be used 
=> read blog 
=> understood properties 
=> understood from the blog and some comments that it can be constructed in O(n) using stacks
=> realized that montonic stack for calculating nge to left and right can be used (1/0 can be used to represent push/pop respectively)

*/

const int MOD = 1e9 + 7;
const int N = 4e4 + 5;
const int inf1 = int(1e9) + 5;
const ll inf2 = ll(1e18) + 5;

#include "floppy.h"

void read_array(int subtask_id, const std::vector<int> &a) {
    int n = sz(a);
    string bits = "";
    stack<int> st;
    vector<int> lx(n,0), rx(n,n-1); 
    
    rep(i,n){
        while(!st.empty() and a[i] > a[st.top()]){
            rx[st.top()] = i-1;
            st.pop();
            bits.pb('0');
        }
        if(!st.empty()){
            lx[i] = st.top()+1;
        }

        st.push(i);
        bits.pb('1');
    }       

    save_to_floppy(bits);
}

template<typename T>
struct sparse_table {
    /*============================*/

    T merge(T a, T b) {
        return max(a,b);
    }

    /*============================*/

    vector<vector<T>> table;
    vector<int> bin_log;
    int LOG = 0;

    sparse_table() {

    }

    sparse_table(vector<T> &a, int n) {
        while ((1 << LOG) <= n) LOG++;

        table = vector<vector<T>>(n, vector<T>(LOG));
        bin_log = vector<int>(n + 1);

        rep(i, n) table[i][0] = a[i];

        rep1(j, LOG - 1) {
            rep(i, n) {
                int jump = 1 << (j - 1);
                if (i + jump >= n) {
                    break;
                }

                table[i][j] = merge(table[i][j - 1], table[i + jump][j - 1]);
            }
        }

        bin_log[1] = 0;
        for (int i = 2; i <= n; ++i) {
            bin_log[i] = bin_log[i / 2] + 1;
        }
    }

    T query(int l, int r) {
        int len = r - l + 1;
        int k = bin_log[len];

        T val1 = table[l][k];
        T val2 = table[r - (1 << k) + 1][k];

        return merge(val1, val2);
    }
};

std::vector<int> solve_queries(int subtask_id, int n,
        const std::string &bits,
        const std::vector<int> &L, const std::vector<int> &R) {

    stack<int> st;
    vector<int> lx(n,0), rx(n,n-1);
    int ptr = 0;

    rep(i,n){
        while(bits[ptr] == '0'){
            rx[st.top()] = i-1;
            st.pop();
            ptr++;
        }

        if(!st.empty()){
            lx[i] = st.top()+1;
        }

        st.push(i);
        ptr++;
    }

    vector<pii> b(n);
    rep(i,n) b[i] = {rx[i],-i};
    sparse_table<pii> sparse(b,n);

    int m = sz(L);
    vector<int> ans(m);

    rep(i,m){
        int l = L[i], r = R[i];
        ans[i] = -sparse.query(l,r).ss;

        // for(int j = l; j <= r; ++j){
        //     if(lx[j] <= l and rx[j] >= r){
        //         ans[i] = j;
        //     }
        // }
    }

    return ans;
}

Compilation message (stderr)

stub.cpp: In function 'void run2()':
stub.cpp:101:30: warning: comparison of integer expressions of different signedness: 'std::vector<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
  101 |     if (query_answers.size() != M) {
      |         ~~~~~~~~~~~~~~~~~~~~~^~~~

• Subtask 1: 7 / 7
• Subtask 2: 21 / 21
• Subtask 3: 72 / 72