Create RMQ.cpp

1 files changed, 20 insertions, 0 deletions

diff --git a/datastructures/RMQ.cpp b/datastructures/RMQ.cpp
new file mode 100644
index 0000000..899db15
--- /dev/null
+++ b/datastructures/RMQ.cpp
@@ -0,0 +1,20 @@
+vector<int> data(RMQ_SIZE);
+vector<vector<int>> rmq(floor(log2(RMQ_SIZE)) + 1, vector<int>(RMQ_SIZE));
+
+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! [a, b)
+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]);
+}