java/data-structures/SegmentTree.java at master · rmnbrgr/java · GitHub

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importjava.util.*;
importjava.lang.*;
importjava.io.*;

classSegmentTree {
intst[];

Segment(int []arr, intn)
 {
intx = (int) Math.ceil((Math.log(n)/Math.log(2)));
intmax_size = 2 *(int) (Math.pow(2,x) - 1);
st = newint[max_size];

constSegmentUtil(arr,0,n-1,0);
 }

intconstSegmentUtil(int[] arr, intss, intse, intsi) {
if (ss == se) {
st[si] = arr[ss];
returnarr[ss];
 }
intmid = getMid(ss, se);
st[si] = max(constSegmentUtil(arr, ss, mid, 2 * si + 1), constSegmentUtil(arr, mid + 1, se, 2 * si + 2));
returnst[si];
 }

intgetMid(ints, inte) {
returns + (e - s) / 2;
 }

intmax(inta, intb) {
if (a > b) {
returna;
 } else {
returnb;
 }
 }

voidprint() {
for (inti = 0; i < st.length; i++) {
System.out.print(st[i]);
 }
 }

intgetMaxUtil(intss, intse, intqs, intqe, intsi) {
if (qs <= ss && qe >= se) {
returnst[si];
 }

if (se < qs || ss > qe) {
return0;
 }

intmid = getMid(ss, se);

returnmax(getMaxUtil(ss, mid, qs, qe, 2 * si + 1), getMaxUtil(mid + 1, se, qs, qe, 2 * si + 2));
 }

intgetMax(intn, intqs, intqe) {

if (qs > qe || qs < 0 || qe > n - 1) {
return -1;
 }

returngetMaxUtil(0, n - 1, qs, qe, 0);
 }

publicstaticvoidmain(String[] args) throwsjava.lang.Exception {
BufferedReaderbr = newBufferedReader(newInputStreamReader(System.in));
intt = Integer.parseInt(br.readLine());// for testcase
String[] temp = br.readLine().split(" ");// taking array as string
int[] arr = newint[t];
for (inti = 0; i < t; i++) // to convert array of string to array of integers
 {
arr[i] = Integer.parseInt(temp[i]);
 }
Segmenttree = newSegment(arr, arr.length);
// tree.print();
intq = Integer.parseInt(br.readLine()); // no of queries
while (q-- != 0) {
String[] temp1 = br.readLine().split(" ");
ints = Integer.parseInt(temp1[0]); // q1
inte = Integer.parseInt(temp1[1]); // q2

System.out.println(tree.getMax(arr.length, s - 1, e - 1)); // maximum in range [q1,q2]
// System.out.println(getMax(arr,n,s,e));
 }
 }
}