Algorithm 递归合并排序
我正在尝试为类编写递归合并排序方法。当我尝试Algorithm 递归合并排序,algorithm,sorting,recursion,merge,stack-overflow,Algorithm,Sorting,Recursion,Merge,Stack Overflow,我正在尝试为类编写递归合并排序方法。当我尝试mergeSort（leftArr）和mergeSort（rightArr）时，我总是遇到堆栈溢出。为什么我的基本情况不起作用 import java.util.Arrays; public class SortingAlgorithms { public static void mergeSort(int[] list){ int mid = list.length / 2; int [] leftArr
mergeSort（leftArr）mergeSort（rightArr）import java.util.Arrays;
public class SortingAlgorithms {
public static void mergeSort(int[] list){
int mid = list.length / 2;
int [] leftArr = new int [mid];
int [] rightArr;
if (mid % 2 == 0) {
rightArr = new int [mid];
}
else{
rightArr = new int [mid + 1];
}
if (leftArr.length < 2 && rightArr.length < 2){
list = mergeHelper(leftArr, rightArr);
}
// copying first half of array
for (int i = 0; i < mid; i++){
leftArr[i] = list[i];
}
// copying second half of array
int placeHolder = 0;
for (int i = mid; i < list.length; i++){
if (placeHolder < rightArr.length) {
rightArr[placeHolder] = list[i];
placeHolder++;
}
}
mergeSort(leftArr);
mergeSort(rightArr);
}
public static int[] mergeHelper(int[] leftArr, int[] rightArr){
int leftIndex = 0;
int rightIndex = 0;
int sortedArrayIndex = 0;
int[] newList = new int[leftArr.length + rightArr.length];
while (leftIndex < leftArr.length || rightIndex < rightArr.length){
if (leftIndex < leftArr.length && rightIndex < rightArr.length){
if(leftArr[leftIndex] > rightArr[rightIndex]){
newList[sortedArrayIndex] = rightArr[rightIndex];
rightIndex++;
sortedArrayIndex++;
}
else {
newList[sortedArrayIndex] = leftArr[leftIndex];
leftIndex++;
sortedArrayIndex++;
}
}
else if (leftIndex < leftArr.length && rightIndex == rightArr.length){
newList[sortedArrayIndex] = leftArr[leftIndex];
leftIndex++;
sortedArrayIndex++;
}
else if (rightIndex < rightArr.length && leftIndex == leftArr.length){
newList[sortedArrayIndex] = rightArr[rightIndex];
rightIndex++;
sortedArrayIndex++;
}
}
return newList;
}
public static void populateArray(int[] list){
for (int i = 0; i < list.length; i++){
list[i] = (int) ((Math.random() * 100));
}
}
public static void main(String[] args){
int [] list = new int [10];
populateArray(list);
System.out.println(Arrays.toString(list));
mergeSort(list);
System.out.println(Arrays.toString(list));
//proof that mergeHelper() works
// int[] left = {1,3,5,7,9};
// System.out.println(Arrays.toString(left));
// int[] right = {0,2,4,6,8};
// System.out.println(Arrays.toString(right));
// System.out.println(Arrays.toString(mergeHelper(left,right)));
}
}
导入java.util.array；
公共类排序算法{
公共静态无效合并排序（int[]列表）{
int mid=list.length/2；
int[]leftArr=新int[mid]；
int[]rightArr；
如果（中间%2==0）{
rightArr=新整数[mid]；
}
否则{
rightArr=新整数[mid+1]；
}
如果（左arr.length<2和右arr.length<2）{
list=mergeHelper（leftArr、rightArr）；
}
//复制数组的前半部分
对于（int i=0；irightArr[rightIndex]）{
newList[SorterDarrayIndex]=rightArr[rightIndex]；
rightIndex++；
索引++；
}
否则{
newList[sortedArrayIndex]=leftArr[leftIndex]；
leftIndex++；
索引++；
}
}
else if（leftIndex rightArr=newint[list.length-mid]###这是一种在c#中使用合并排序的方法，带有递归##
## This is a way to use merge sort in c#, with recursion. ##
static void Main(string[] args)
{
List<int> list = new List<int>();
int m = int.Parse(Console.ReadLine());
for (int i = 0; i < m; i++)
{
int p = int.Parse(Console.ReadLine());
list.Add(p);
}
Console.WriteLine(String.Join(",", MergeSort(list)));
}
static List<int> MergeSort(List<int> array)
{
List<int> output = new List<int>();
if (array.Count == 1)
{
return array;
}
if (array.Count == 2)
{
if (array[0] > array[1])
{
int a = array[1];
array[1] = array[0];
array[0] = a;
return array;
}
else
{
return array;
}
}
else
{
List<int> firstList = new List<int>();
List<int> secondList = new List<int>();
for (int i = 0; i < array.Count / 2; i++)
{
firstList.Add(array[i]);
secondList.Add(array[i + array.Count / 2]);
}
if (array.Count % 2 != 0)
{
secondList.Add(array[array.Count - 1]);
}
firstList = MergeSort(firstList);
secondList = MergeSort(secondList);
int k = 0;
int j = 0;
int size = firstList.Count + secondList.Count;
int markerFirst = firstList.Count;
int markerSecond = secondList.Count;
for (int i = 0; i < size; i++)
{
if (k == markerFirst)
{
output.Add(secondList[j]);
j++;
continue;
}
if (j == markerSecond)
{
output.Add(firstList[k]);
k++;
continue;
}
if (firstList[k] < secondList[j])
{
output.Add(firstList[k]);
k++;
}
else
{
output.Add(secondList[j]);
j++;
}
}
}
return output;
}
}
}
静态void Main（字符串[]参数）
{
列表=新列表（）；
int m=int.Parse（Console.ReadLine（））；
for（int i=0；i数组[1]）
{
int a=数组[1]；
数组[1]=数组[0]；
数组[0]=a；
返回数组；
}
其他的
{
返回数组；
}
}
其他的
{
List firstList=新列表（）；
List secondList=新列表（）；
for（int i=0；i
您的代码存在一些问题：
1） 在“mergeSort”方法中，没有条件停止下面的代码这样的递归。您会收到stackoverflows，因为您的代码处于无限循环中。在“mergeSort”方法的第一行添加此代码
以更简单的方式遵循代码
import java.util.Arrays;
public class MergeSort {
public static void main(String[] args) {
Integer[] itens = {2,6,4,9,1,3,8,7,0};
Integer[] tmp = new Integer[itens.length];
int left = 0;
int right = itens.length - 1;
mergeSort(itens, tmp, left, right);
System.out.println(Arrays.toString(itens));
}
private static void mergeSort(Integer[] itens, Integer[] tmpArray, int left, int right) {
if(itens == null || itens.length == 0 || left >= right){
return;
}
int midle = (left + right) / 2;
mergeSort(itens, tmpArray, left, midle);
mergeSort(itens, tmpArray, midle + 1, right);
merge(itens, tmpArray, left, midle + 1, right);
}
private static void merge(Integer[] itens, Integer[] tmpArray, int left, int right, int rightEnd) {
int leftEnd = right - 1;
int tmpIndex = left;
while (left <= leftEnd && right <= rightEnd){
if (itens[left] < itens[right] ){
tmpArray[tmpIndex++] = itens[left++];
} else {
tmpArray[tmpIndex++] = itens[right++];
}
}
while (left <= leftEnd) { // Copy rest of LEFT half
tmpArray[tmpIndex++] = itens[left++];
}
while (right <= rightEnd) { // Copy rest of RIGHT half
tmpArray[tmpIndex++] = itens[right++];
}
while(rightEnd >= 0){ // Copy TEMP back
itens[rightEnd] = tmpArray[rightEnd--];
}
}
}
导入java.util.array；
酒吧
int[] rightArr = new int [list.length - mid];
// if (mid % 2 == 0) {
// rightArr = new int[mid];
// } else {
// rightArr = new int[mid + 1];
// }
import java.util.Arrays;
public class MergeSort {
public static void main(String[] args) {
Integer[] itens = {2,6,4,9,1,3,8,7,0};
Integer[] tmp = new Integer[itens.length];
int left = 0;
int right = itens.length - 1;
mergeSort(itens, tmp, left, right);
System.out.println(Arrays.toString(itens));
}
private static void mergeSort(Integer[] itens, Integer[] tmpArray, int left, int right) {
if(itens == null || itens.length == 0 || left >= right){
return;
}
int midle = (left + right) / 2;
mergeSort(itens, tmpArray, left, midle);
mergeSort(itens, tmpArray, midle + 1, right);
merge(itens, tmpArray, left, midle + 1, right);
}
private static void merge(Integer[] itens, Integer[] tmpArray, int left, int right, int rightEnd) {
int leftEnd = right - 1;
int tmpIndex = left;
while (left <= leftEnd && right <= rightEnd){
if (itens[left] < itens[right] ){
tmpArray[tmpIndex++] = itens[left++];
} else {
tmpArray[tmpIndex++] = itens[right++];
}
}
while (left <= leftEnd) { // Copy rest of LEFT half
tmpArray[tmpIndex++] = itens[left++];
}
while (right <= rightEnd) { // Copy rest of RIGHT half
tmpArray[tmpIndex++] = itens[right++];
}
while(rightEnd >= 0){ // Copy TEMP back
itens[rightEnd] = tmpArray[rightEnd--];
}
}
}