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Copy pathRangeMinimumQuery.java
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68 lines (58 loc) · 2.01 KB
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import java.io.BufferedReader;
import java.io.InputStreamReader;
public class RangeMinimumQuery {
public static void main(String[] args) throws Exception {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
String line = br.readLine();
int N = Integer.valueOf(line.split(" ")[0]);
int M = Integer.valueOf(line.split(" ")[1]);
int values[] = new int[N];
line = br.readLine();
int i = 0;
for (String S : line.split(" "))
values[i++] = Integer.valueOf(S);
SegmentTree segmentTree = new SegmentTree(N);
segmentTree.buildTree(values, 0, N - 1, 0);
for (int l = 0; l < M; l++) {
line = br.readLine();
int left = Integer.valueOf(line.split(" ")[0]);
int right = Integer.valueOf(line.split(" ")[1]);
System.out.println(segmentTree.query(values, left, right));
}
}
}
class SegmentTree {
int[] tree;
private final int INF = Integer.MAX_VALUE - 1;
private final int STARTINDEX = 0;
private final int ENDINDEX;
public SegmentTree(int size) {
ENDINDEX = size - 1;
int height = 2 * (int) Math.pow(2, Math.ceil(Math.log(size) / Math.log(2)));
tree = new int[height];
for (int i = 0; i < height; i++)
tree[i] = INF;
}
public void buildTree(int[] values, int left, int right, int root) {
if (left == right) {
tree[root] = values[left];
return;
}
int mid = (left + right) / 2;
buildTree(values, left, mid, 2 * root + 1);
buildTree(values, mid + 1, right, 2 * root + 2);
tree[root] = Math.min(tree[2 * root + 1], tree[2 * root + 2]);
}
public int query(int[] values, int qs, int qe) {
return queryUtil(values, STARTINDEX, ENDINDEX, qs, qe, 0);
}
private int queryUtil(int[] values, int l, int r, int qs, int qe, int root) {
int left = 2 * root + 1, right = left + 1;
if (l >= qs && r <= qe)
return tree[root];
if (l > qe || r < qs)
return INF;
int mid = (l + r) / 2;
return Math.min(queryUtil(values, l, mid, qs, qe, left), queryUtil(values, mid + 1, r, qs, qe, right));
}
}