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Copy pathmergeKSortedLists.cpp
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187 lines (157 loc) · 4.36 KB
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// Source : https://oj.leetcode.com/problems/merge-k-sorted-lists/
// Author : Hao Chen
// Date : 2014-07-06
/**********************************************************************************
*
* Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity.
*
*
**********************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <iostream>
#include <vector>
using namespace std;
struct ListNode {
int val;
ListNode *next;
ListNode(int x) : val(x), next(NULL) {}
};
ListNode *mergeTwoLists(ListNode* head1, ListNode* head2);
ListNode *mergeTwoLists01(ListNode* head1, ListNode* head2);
ListNode *mergeTwoLists02(ListNode* head1, ListNode* head2);
ListNode *mergeKLists(vector<ListNode *> &lists) {
ListNode *p, *p1, *p2;
while(lists.size()>1){
p1 = lists.back();
lists.pop_back();
p2 = lists.back();
lists.pop_back();
p = mergeTwoLists(p1, p2);
lists.insert(lists.begin(), p);
}
return lists.size()==1 ? lists[0] : NULL;
/* the following method is not fast enough! */
/*
ListNode* pHead = NULL;
for (int i=0; i<lists.size(); i++){
pHead = mergeTwoLists(pHead, lists[i]);
}
return pHead;
*/
}
static int n=0;
ListNode *mergeTwoLists(ListNode* head1, ListNode* head2){
if (n){
//cout << "------ method 01 ------" <<endl;
return mergeTwoLists01(head1, head2);
}
//cout << "------ method 02 ------" <<endl;
return mergeTwoLists02(head1, head2);
}
/*======================================================================*/
/* Method One */
/*======================================================================*/
//#define INT_MAX 2147483647
//#define INT_MIN (-INT_MAX - 1)
ListNode *mergeTwoLists01(ListNode* head1, ListNode* head2){
ListNode *p1 = head1, *p2=head2;
static ListNode dummy(0);
dummy.next = p1;
ListNode *prev = &dummy;
while(p1 && p2){
if(p1->val < p2->val){
prev = p1;
p1 = p1->next;
}else{
prev->next = p2;
p2 = p2->next;
prev = prev->next;
prev->next = p1;
}
}
if (p2){
prev->next = p2;
}
return dummy.next;
}
/*======================================================================*/
/* Method Two */
/*======================================================================*/
void TakeOutNode(ListNode*& head, ListNode*& tail, ListNode*& p);
ListNode *mergeTwoLists02(ListNode* head1, ListNode* head2) {
ListNode *p1 = head1, *p2=head2;
ListNode *pHead = NULL, *pTail=NULL;
while(p1 && p2){
if(p1->val < p2->val){
TakeOutNode(pHead, pTail, p1);
}else{
TakeOutNode(pHead, pTail, p2);
}
}
ListNode *p=NULL;
if (p1){
p = p1;
}else if (p2){
p = p2;
}
if (pHead==NULL){
return p;
}
pTail->next = p;
return pHead;
}
void TakeOutNode(ListNode*& head, ListNode*& tail, ListNode*& p){
ListNode *pNext = p->next;
if (head==NULL){
head = tail = p;
}else{
tail->next = p;
tail = p;
}
p->next = NULL;
p = pNext;
}
void printList(ListNode* h)
{
while(h!=NULL){
printf("%d ", h->val);
h = h->next;
}
printf("\n");
}
ListNode* createList(int a[], int n)
{
ListNode *head=NULL, *p=NULL;
for(int i=0; i<n; i++){
if (head == NULL){
head = p = new ListNode(a[i]);
}else{
p->next = new ListNode(a[i]);
p = p->next;
}
}
return head;
}
int main(int argc, char**argv)
{
srand(time(0));
if (argc>1){
n = atoi(argv[1]) % 2;
}
int a[] = {1,3,5,6,7,10};
int b[] = {0,4,6,8,9,11,20,30,40};
ListNode* p1 = createList(a, sizeof(a)/sizeof(int));
ListNode* p2 = createList(b, sizeof(b)/sizeof(int));
printList( mergeTwoLists(p1,p2) );
//mergeTwoLists(p1,p2) ;
vector<ListNode*> v;
for(int i=0; i<10240; i++) {
v.push_back(new ListNode(random()%100));
}
printList( mergeKLists(v) );
//mergeKLists(v);
cout << "method " << n+1 << endl;
return 0;
}