我一直在尝试实现一个合并排序，将数组分为三个部分而不是两个部分。我似乎在某个地方遇到了 StackOverflow 异常。有人可以帮我找到它吗？ (SO 在第 54、58、59 行报告)
导入java.util.; 导入java.io。;
类合并排序问题{
// merges sorted subarrays A[start...firstThird], A[firstThird+1,secondThird], and A[secondThird+1,stop]
public static void mergeThreeWay(int A[], int start, int firstThird, int secondThird, int stop)
{
int indexLeft = start;
int indexFirstThird = firstThird+1;
int indexSecondThird = secondThird+1;
int tmp1[] = new int[A.length];
int tmpIndex = start;
while(tmpIndex <= firstThird){
if (indexFirstThird < firstThird || (indexLeft <= firstThird && A[indexLeft] <= A[indexFirstThird])){
tmp1[tmpIndex] = A[indexLeft];
indexLeft++;
}else if(indexSecondThird < secondThird || (indexFirstThird <= secondThird && A[firstThird] <= A[indexSecondThird])){
tmp1[tmpIndex] = A[indexFirstThird];
indexFirstThird++;
}else{
tmp1[tmpIndex] = A[indexSecondThird];
indexSecondThird = indexSecondThird + 1;
}
tmpIndex++;
}
int i = 0;
for(int temp : tmp1){
A[i] = temp;
i++;
}
}
// sorts A[start...stop]
public static void mergeSortThreeWay(int A[], int start, int stop) {
if (start < stop){
int firstThird = (start+stop)/3;
int secondThird = 2*(firstThird);
mergeSortThreeWay(A, start, firstThird);
mergeSortThreeWay(A, firstThird+1, secondThird);
mergeSortThreeWay(A, secondThird+1, stop);
mergeThreeWay(A, start, firstThird, secondThird, stop);
}
}
public static void main (String args[]) throws Exception {
int myArray[] = {8,3,5,7,9,2,3,5,5,6};
mergeSortThreeWay(myArray,0,myArray.length-1);
System.out.println("Sorted array is:\n");
for (int i=0;i<myArray.length;i++) {
System.out.println(myArray[i]+" ");
}
}
}
最佳答案
您的 firstThird 和 secondThird 变量在 mergeSortThreeWay 执行中的某个点不会将值从一次迭代更改为另一次迭代。
在你的例子中，我得到:
start=4 stop=6
firstThird=3 secondThird=6
start=4 stop=6
firstThird=3 secondThird=6
// so java.lang.StackOverflowError
计算 firstThird 和 secondThird 的公式似乎不起作用。尝试使用
firstThird = (stop-start)/3 + start;
secondThird = 2*(stop-start)/3 + start;
关于java - 归并排序实现给出了 StackOverflow，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/19044357/