JZ-C-15

剑指offer第十五题:链表中倒数第K个结点

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//============================================================================
// Name        : JZ-C-15.cpp
// Author      : Laughing_Lz
// Version     :
// Copyright   : All Right Reserved
// Description : 链表中倒数第K个结点
//============================================================================
 
#include <iostream>
#include "List.h"
#include <stdio.h>
using namespace std;
 
ListNode* FindKthToTail(ListNode* node, unsigned int k) {
    if (k == 0 || node == NULL) {
        return NULL;
    }
    ListNode* head = node;
    ListNode* follow = node;
    for (unsigned int i = 0; i < k - 1; i++) {
        if (head->m_pNext == NULL) {
            return NULL;
        } else {
            head = head->m_pNext;
        }
    }
    while (head->m_pNext != NULL) {
        head = head->m_pNext;
        follow = follow->m_pNext;
    }
    return follow;
}
 
// ====================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: NULL.\n");
    ListNode* pNode = FindKthToTail(NULL, 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: NULL.\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: NULL.\n");
    ListNode* pNode = FindKthToTail(pNode1, 0);
    PrintListNode(pNode);
 
    DestroyList(pNode1);
}
 
int main(int argc, char** argv) {
    Test1();
    Test2();
    Test3();
    Test4();
    Test5();
    Test6();
 
    return 0;
}

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