I am trying to reverse a sublist in a List using the indices provided in a multidimensional List. I don’t have much experience using multidimensional lists/arrays. I don’t understand why this doesn’t work.
JavaScript
x
/*
Given a List<Integer> list and List<List<Integer>> operations
reverse the sublist and print out the list after all the operations have been done.
Ex: [5, 3, 2, 1, 3]
[[0,1], [1, 3]]
*/
import java.util.*;
public class ReverseParameters {
public static void main(String[] args) {
List<Integer> list = Arrays.asList(5, 3, 2, 1, 3);
List<List<Integer>> operations = new ArrayList<>(2);
for(int i= 0; i < 3; i++){
operations.add(new ArrayList<>());
}
operations.get(0).add(1);
operations.get(1).add(3);
subList(list, operations);
}
public static void subList (List<Integer> list, List<List<Integer>> operations) {
System.out.println(list);
int vertCount = operations.size();
for (int i = 0; i < vertCount; i++) {
int edgeCount = operations.get(i).size();
for (int j = 0; j < edgeCount; j++) {
int startInd = i;
int endInd = operations.get(i).get(j);
int shift = endInd - startInd;
int right = Math.min(i + shift - 1, list.size() - 1);
int temp = 0;
while (startInd < right) {
temp = list.get(startInd);
list.set(startInd, list.get(right));
list.set(right, temp);
startInd+=1;
right-=1;
}
System.out.println();
System.out.printf(" %d %d%n", startInd, endInd);
System.out.println();
}
}
System.out.println(list);
}
}
The output of this code using [[0,1], [1, 3]] as the indecies is:
JavaScript
[5, 2, 3, 1, 3]
but it should be:
JavaScript
[3, 1, 2, 5, 3]
Can someone please help point me in the right direction?
Advertisement
Answer
This can be done as simple as this.
JavaScript
public class Main
{
public static void main(String[] args)
{
//Given a List<Integer> list and List<List<Integer>> operations
//reverse the sublist and print out the list after all the operations have been done.
//Ex: [5, 3, 2, 1, 3]
// [[0,1], [1, 3]]
//Target: [3, 1, 2, 5, 3]
//Steps:
// 0 1 2 3 4 (Indices)
//###############
//[5, 3, 2, 1, 3]
//[3, 5, 2, 1, 3] // Swap index of 0 and 1.
//[3, 1, 2, 5, 3] // Swap index of 1 and 3.
List<Integer> list = Arrays.asList(5, 3, 2, 1, 3);
List<List<Integer>> listOfList = new ArrayList<List<Integer>>(2);
listOfList.add(Arrays.asList(0, 1));
listOfList.add(Arrays.asList(1, 3));
for(int i=0; i < listOfList.size(); ++i) {
final int indexA = listOfList.get(i).get(0); //[0 , [1
final int indexB = listOfList.get(i).get(1); // 1], 3]
//Swap the indices.
final int tmpValue = list.get(indexA);
list.set(indexA, list.get(indexB));
list.set(indexB, tmpValue);
}
System.out.println(list);
//[3, 1, 2, 5, 3]
}
}