datastructures/RMQ.cpp


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vector<int> data(RMQ_SIZE);
vector<vector<int>> rmq(floor(log2(RMQ_SIZE)) + 1, vector<int>(RMQ_SIZE));

//Runtime: O(n*log(n))
void initRMQ() {
	for(int i = 0, s = 1, ss = 1; s <= RMQ_SIZE; ss=s, s*=2, i++) {
		for(int l = 0; l + s <= RMQ_SIZE; l++) {
			if(i == 0) rmq[0][l] = l;
			else {
				int r = l + ss;
				rmq[i][l] = (data[rmq[i-1][l]] <= data[rmq[i-1][r]] ? rmq[i-1][l] : rmq[i-1][r]);
			}
		}
	}
}
//returns index of minimum! [l, r)
//Runtime: O(1)
int queryRMQ(int l, int r) {
	if(l >= r) return l;
	int s = floor(log2(r-l)); r = r - (1 << s);
	return (data[rmq[s][l]] <= data[rmq[s][r]] ? rmq[s][l] : rmq[s][r]);
}