对链表数组进行合并排序
对链表数组进行合并排序
提问于 2019-03-01 08:30:24
我正在尝试合并、排序一个数组的每个元素，它是一个链表的头。
//for each element in array
for(int i=0; i<MAX_SIZE; i++){
//NOTE: this current element (i) holds a linked list...sort it
//merge function should accept head of linked list which is this element
mergeSort(&inventory[i]);
}下面是我的合并排序函数，它递归地调用自己...
void mergeSort(data** A){
data* head = *A; //head is begining of A
data* r;
data* l;
//base case ... if linked list length is 0 or 1
if(head == nullptr || head->next == nullptr){
return;
}
//divide linked list into halves
split(head, &r, &l);
//r holds first half of linked list
//l holds left second half of linked list
mergeSort(&r);
mergeSort(&l);
*A = merge(r,l); //merge into linked list A
}下面是split算法。
void split(data* source, data** R, data** L){ //source is head of this linked list
data* slow = source;
data* fast = source->next;
while(fast->next->next){ //while fast has two nodes after it
fast= fast->next;
slow = slow->next;
}
*L = source;
*R = slow->next;
slow->next = nullptr;
}最后我将这些段合并到链表A中，下面的函数返回链表的头部并设置为A…
data* merge(data* R, data* L){
data* result = nullptr;
//base cases
if(R == nullptr){
return R;
}
else if(L == nullptr){
return L;
}
if(R->pnum <= L->pnum){
result = R;
result->next = merge(R->next, L);
}
else{
result = L;
result->next = merge(L, R->next);
}
return result;}
当我尝试用一个简单的打印函数打印整个数组时，代码成功运行，但没有打印出来，我认为合并代码永远不会停止运行。终端中没有显示错误(使用xcode的即时消息)。
对如何解决这个问题有什么建议吗？谢谢!
回答 1
Stack Overflow用户
发布于 2019-03-01 13:04:25
请尝试使用此合并排序代码。
/* C program for Merge Sort */
#include<stdlib.h>
#include<stdio.h>
// Merges two subarrays of arr[].
// First subarray is arr[l..m]
// Second subarray is arr[m+1..r]
void merge(int arr[], int l, int m, int r)
{
int i, j, k;
int n1 = m - l + 1;
int n2 = r - m;
/* create temp arrays */
int L[n1], R[n2];
/* Copy data to temp arrays L[] and R[] */
for (i = 0; i < n1; i++)
L[i] = arr[l + i];
for (j = 0; j < n2; j++)
R[j] = arr[m + 1+ j];
/* Merge the temp arrays back into arr[l..r]*/
i = 0; // Initial index of first subarray
j = 0; // Initial index of second subarray
k = l; // Initial index of merged subarray
while (i < n1 && j < n2)
{
if (L[i] <= R[j])
{
arr[k] = L[i];
i++;
}
else
{
arr[k] = R[j];
j++;
}
k++;
}
/* Copy the remaining elements of L[], if there
are any */
while (i < n1)
{
arr[k] = L[i];
i++;
k++;
}
/* Copy the remaining elements of R[], if there
are any */
while (j < n2)
{
arr[k] = R[j];
j++;
k++;
}
}
/* l is for left index and r is right index of the
sub-array of arr to be sorted */
void mergeSort(int arr[], int l, int r)
{
if (l < r)
{
// Same as (l+r)/2, but avoids overflow for
// large l and h
int m = l+(r-l)/2;
// Sort first and second halves
mergeSort(arr, l, m);
mergeSort(arr, m+1, r);
merge(arr, l, m, r);
}
}
/* UTILITY FUNCTIONS */
/* Function to print an array */
void printArray(int A[], int size)
{
int i;
for (i=0; i < size; i++)
printf("%d ", A[i]);
printf("\n");
}
/* Driver program to test above functions */
int main()
{
int arr[] = {12, 11, 13, 5, 6, 7};
int arr_size = sizeof(arr)/sizeof(arr[0]);
printf("Given array is \n");
printArray(arr, arr_size);
mergeSort(arr, 0, arr_size - 1);
printf("\nSorted array is \n");
printArray(arr, arr_size);
return 0;
} 页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/54936303
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