我正在嘗試使用多維串列中提供的索引反轉串列中的子串列。我沒有太多使用多維串列/陣列的經驗。我不明白為什么這不起作用。
/*
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);
}
}
使用 [[0,1], [1, 3]] 作為 indecies 的這段代碼的輸出是：
[5, 2, 3, 1, 3]
但它應該是：
[3, 1, 2, 5, 3]
有人可以幫我指出正確的方向嗎？
uj5u.com熱心網友回復：
您使用不必要的變數使代碼過于復雜，從而難以找到問題。請使用更簡單的代碼和說明：
public static void main(String[] args) {
List<Integer> list = Arrays.asList(5, 3, 2, 1, 3);
List<List<Integer>> operations = new ArrayList<>(2);
// Initialize your operations
operations.add(Arrays.asList(0,1));
operations.add(Arrays.asList(1,3));
subList(list, operations);
}
public static void subList (List<Integer> list, List<List<Integer>> operations) {
// You just iterate over the operations
for (List<Integer> operation : operations) {
// For each operation, store left and right indexes.
int left = operation.get(0);
int right = operation.get(1);
// Iterate until both indexes find each other
while (left < right) {
// Swap left and right elements in input list
int aux = list.get(left);
list.set(left, list.get(right));
list.set(right, aux);
// Now you move your indexes
left;
--right;
}
}
System.out.println(list);
}
請注意，根據問題的要求，您可能還需要驗證操作索引是否在串列邊界內，以便您最終不會收到 ArrayIndexOutOfBoundsException。所以要始終小心邊緣情況。
uj5u.com熱心網友回復：
這可以像這樣簡單地完成。
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]
}
}
uj5u.com熱心網友回復：
您可以通過List.subList()獲取子集，并通過Collections.reverse()反向。
static void reverseSubsets(List<Integer> list, List<List<Integer>> subsets) {
for (List<Integer> subset : subsets)
Collections.reverse(list.subList(subset.get(0), subset.get(1) 1));
}
public static void main(String[] args) {
List<Integer> list = Arrays.asList(5, 3, 2, 1, 3);
List<List<Integer>> subsets = List.of(List.of(0, 1), List.of(1, 3));
reverseSubsets(list, subsets);
System.out.println(list);
}
輸出：
[3, 1, 2, 5, 3]
注意：
toIndex在List.subList(int fromIndex, int toIndex) 中是 subList 的專屬高端。因此，您必須將 1 添加到subset.get(1).
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