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047_KthNodeFromEnd.cpp
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// Coding Interviews: Questions, Analysis & Solutions
// Harry He
#include <stdio.h>
#include "..\Utility\List.h"
ListNode* FindKthToTail(ListNode* pListHead, unsigned int k)
{
if(pListHead == NULL || k == 0)
return NULL;
ListNode *pAhead = pListHead;
ListNode *pBehind = NULL;
for(unsigned int i = 0; i < k - 1; ++ i)
{
if(pAhead->m_pNext != NULL)
pAhead = pAhead->m_pNext;
else
{
return NULL;
}
}
pBehind = pListHead;
while(pAhead->m_pNext != NULL)
{
pAhead = pAhead->m_pNext;
pBehind = pBehind->m_pNext;
}
return pBehind;
}
// ==================== Test Code ====================
void Test(char* testName, ListNode* pHead, int index, int expected, bool isNull)
{
if(testName != NULL)
printf("%s begins: ", testName);
ListNode* pNode = FindKthToTail(pHead, index);
if((isNull && pNode == NULL) || (!isNull && (pNode->m_nValue == expected)))
printf("Passed.\n");
else
printf("FAILED.\n");
}
// The target node is inside the list
void Test1()
{
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);
Test("Test1", pNode1, 2, 4, false);
DestroyList(pNode1);
}
// The target node is the tail node
void Test2()
{
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);
Test("Test2", pNode1, 1, 5, false);
DestroyList(pNode1);
}
// The target node is the head node
void Test3()
{
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);
Test("Test3", pNode1, 5, 1, false);
DestroyList(pNode1);
}
// empty list
void Test4()
{
Test("Test4", NULL, 100, 1, true);
}
// the input k is greater than the number of nodes in a list
void Test5()
{
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);
Test("Test5", pNode1, 6, 1, true);
DestroyList(pNode1);
}
// the input k is 0
void Test6()
{
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);
Test("Test6", pNode1, 0, 1, true);
DestroyList(pNode1);
}
int main(int argc, char* argv[])
{
Test1();
Test2();
Test3();
Test4();
Test5();
Test6();
return 0;
}