Cod sursa(job #820062)

Utilizator nimeniaPaul Grigoras nimenia Data 19 noiembrie 2012 23:29:38
Problema Range minimum query Scor 30
Compilator cpp Status done
Runda Arhiva educationala Marime 1.07 kb
#include <iostream>
#include <fstream>
#include <cmath>

using namespace std;



int main() {

	freopen("rmq.in","r",stdin);
	freopen("rmq.out", "w", stdout);

	long int n, m;
	scanf("%ld %ld", &n, &m);

	long int nums[n + 1];

	for (int i = 1; i <= n; i++)
		scanf("%ld", &nums[i]);

	// pre process rmq
	long int log2[n + 2];
	log2[1] = log2[0] = 0;
	for (long int i = 2; i<= n + 1; i++){
		log2[i] = log2[i/2]+1;
	}

	long int rmq[n + 1][log2[n+1]];

	for (long int i = 1; i <= n; i++) {	
		rmq[i][0] = i; // intervals of length 2^0 = 1
	}

	for (long int j = 1; (1 << j) <= n; j++) {
		for (long int i = 1; i + (1 << j) - 1 <= n; i++) {
			int minSeg1 = rmq[i][j-1];  
			int minSeg2 = rmq[ i  + (1 <<(j-1))][j-1];
			if (nums[minSeg1] < nums[minSeg2]) {
				rmq[i][j] = minSeg1;
			} else {
				rmq[i][j] = minSeg2;
			}
		}
	}

	long int a, b;
	for (long int i = 0; i < m; i++) {

		scanf("%ld %ld", &a, &b);
		// process query
		long int k = log2[b - a + 1];
		long int res = min(nums[rmq[a][k]], 
		              nums[rmq[b - (1 << k) + 1][k]]);

		printf("%ld\n", res);
	}

	return 0;
}