Cod sursa(job #2824817)

Utilizator Snake2003lalallalal Snake2003 Data 3 ianuarie 2022 15:53:20
Problema Range minimum query Scor 0
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 1.02 kb
#include <bits/stdc++.h>

using namespace std;

ifstream fin("rmq.in");
ofstream fout("rmq.out");

const int MAX_N = 100005;
const int LOG = 17; // 1 << 17 = ~131k

int m[MAX_N][LOG];
int a[MAX_N];
int Log_2[MAX_N];

int query(int L, int R)
{
    int len = R - L + 1;
    // take log2(len)
    int k = Log_2[len];
    return min(m[L][k], m[R - (1 << k)][k]);
}

int main()
{
    // citire

    int n, Q;
    fin >> n >> Q;

    Log_2[1] = 0; // 1 << 0 = 1
    for(int i = 2; i <= n; i ++)
        Log_2[i] = Log_2[i / 2] + 1;

    for(int i = 0; i < n; i ++)
    {
        fin >> a[i];
        m[i][0] = a[i];
    }

    // preprocesare
    for(int j = 1; j < LOG; j ++) // 1, 2, 4, 8, 16, ..
        for(int i = 0; i + (1 << j) - 1 < n; i ++)
        {
            m[i][j] = min(m[i][j - 1], m[i + (1 << (j - 1))][j - 1]);
        }
    // queries
    for(int i = 0; i < Q; i ++)
    {
        int R, L;
        fin >> L >> R;
        fout << query(L, R) << "\n";
    }
    return 0;
}