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22_KthNodeFromEnd.cpp
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183 lines (150 loc) · 4.84 KB
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/*******************************************************************
Copyright(c) 2016, Harry He
All rights reserved.
Distributed under the BSD license.
(See accompanying file LICENSE.txt at
https://github.com/zhedahht/CodingInterviewChinese2/blob/master/LICENSE.txt)
*******************************************************************/
//==================================================================
// 《剑指Offer——名企面试官精讲典型编程题》代码
// 作者：何海涛
//==================================================================
// 面试题22：链表中倒数第k个结点
// 题目：输入一个链表，输出该链表中倒数第k个结点。为了符合大多数人的习惯，
// 本题从1开始计数，即链表的尾结点是倒数第1个结点。例如一个链表有6个结点，
// 从头结点开始它们的值依次是1、2、3、4、5、6。这个链表的倒数第3个结点是
// 值为4的结点。
#include <cstdio>
#include "./Utilities/List.h"
ListNode* FindKthToTail(ListNode* pListHead, unsigned int k)
{
if(pListHead == nullptr || k == 0)
return nullptr;
ListNode *pAhead = pListHead;
ListNode *pBehind = nullptr;
for(unsigned int i = 0; i < k - 1; ++ i)
{
if(pAhead->m_pNext != nullptr)
pAhead = pAhead->m_pNext;
else
{
return nullptr;
}
}
pBehind = pListHead;
while(pAhead->m_pNext != nullptr)
{
pAhead = pAhead->m_pNext;
pBehind = pBehind->m_pNext;
}
return pBehind;
}
// ====================测试代码====================
// 测试要找的结点在链表中间
void Test1()
{
printf("=====Test1 starts:=====\n");
ListNode* pNode1 = CreateListNode(1);
ListNode* pNode2 = CreateListNode(2);
ListNode* pNode3 = CreateListNode(3);
ListNode* pNode4 = CreateListNode(4);
ListNode* pNode5 = CreateListNode(5);
ConnectListNodes(pNode1, pNode2);
ConnectListNodes(pNode2, pNode3);
ConnectListNodes(pNode3, pNode4);
ConnectListNodes(pNode4, pNode5);
printf("expected result: 4.\n");
ListNode* pNode = FindKthToTail(pNode1, 2);
PrintListNode(pNode);
DestroyList(pNode1);
}
// 测试要找的结点是链表的尾结点
void Test2()
{
printf("=====Test2 starts:=====\n");
ListNode* pNode1 = CreateListNode(1);
ListNode* pNode2 = CreateListNode(2);
ListNode* pNode3 = CreateListNode(3);
ListNode* pNode4 = CreateListNode(4);
ListNode* pNode5 = CreateListNode(5);
ConnectListNodes(pNode1, pNode2);
ConnectListNodes(pNode2, pNode3);
ConnectListNodes(pNode3, pNode4);
ConnectListNodes(pNode4, pNode5);
printf("expected result: 5.\n");
ListNode* pNode = FindKthToTail(pNode1, 1);
PrintListNode(pNode);
DestroyList(pNode1);
}
// 测试要找的结点是链表的头结点
void Test3()
{
printf("=====Test3 starts:=====\n");
ListNode* pNode1 = CreateListNode(1);
ListNode* pNode2 = CreateListNode(2);
ListNode* pNode3 = CreateListNode(3);
ListNode* pNode4 = CreateListNode(4);
ListNode* pNode5 = CreateListNode(5);
ConnectListNodes(pNode1, pNode2);
ConnectListNodes(pNode2, pNode3);
ConnectListNodes(pNode3, pNode4);
ConnectListNodes(pNode4, pNode5);
printf("expected result: 1.\n");
ListNode* pNode = FindKthToTail(pNode1, 5);
PrintListNode(pNode);
DestroyList(pNode1);
}
// 测试空链表
void Test4()
{
printf("=====Test4 starts:=====\n");
printf("expected result: nullptr.\n");
ListNode* pNode = FindKthToTail(nullptr, 100);
PrintListNode(pNode);
}
// 测试输入的第二个参数大于链表的结点总数
void Test5()
{
printf("=====Test5 starts:=====\n");
ListNode* pNode1 = CreateListNode(1);
ListNode* pNode2 = CreateListNode(2);
ListNode* pNode3 = CreateListNode(3);
ListNode* pNode4 = CreateListNode(4);
ListNode* pNode5 = CreateListNode(5);
ConnectListNodes(pNode1, pNode2);
ConnectListNodes(pNode2, pNode3);
ConnectListNodes(pNode3, pNode4);
ConnectListNodes(pNode4, pNode5);
printf("expected result: nullptr.\n");
ListNode* pNode = FindKthToTail(pNode1, 6);
PrintListNode(pNode);
DestroyList(pNode1);
}
// 测试输入的第二个参数为0
void Test6()
{
printf("=====Test6 starts:=====\n");
ListNode* pNode1 = CreateListNode(1);
ListNode* pNode2 = CreateListNode(2);
ListNode* pNode3 = CreateListNode(3);
ListNode* pNode4 = CreateListNode(4);
ListNode* pNode5 = CreateListNode(5);
ConnectListNodes(pNode1, pNode2);
ConnectListNodes(pNode2, pNode3);
ConnectListNodes(pNode3, pNode4);
ConnectListNodes(pNode4, pNode5);
printf("expected result: nullptr.\n");
ListNode* pNode = FindKthToTail(pNode1, 0);
PrintListNode(pNode);
DestroyList(pNode1);
}
int main(int argc, char* argv[])
{
Test1();
Test2();
Test3();
Test4();
Test5();
Test6();
return 0;
}