美团网2014年校园招聘笔试题（哈工大）

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2014年美团网校园招聘研发类笔试
1、一堆硬币，一个机器人，如果是反的就翻正，如果是正的就抛掷一次，无穷多次后，求正反的比例

设正比例为x,反的比例就是1-x；现在根据反的翻正，正的重新投掷，那么正的就为1-x+(1/2*x),反的就为1/2*x.无穷次会达到平衡，那么1-x就应该等于1/2*x。所以x为2/3，即正的为2/3

4、链表翻转。给出一个链表和一个数k，比如链表1→2→3→4→5→6，k=2，则翻转后2→1→4→3→6→5，若k=3,翻转后3→2→1→6→5→4，若k=4，翻转后4→3→2→1→5→6，用程序实现

#include <iostream>using namespace std;struct ListNode{int m_nValue;ListNode *m_pNext;};ListNode* CreateList(int val){ListNode *pHead = new ListNode;pHead->m_nValue = val;pHead->m_pNext = NULL;return pHead;}void InsertNode(ListNode **pHead, int val){ListNode *pNode = new ListNode;pNode->m_nValue = val;pNode->m_pNext = NULL;while ((*pHead)->m_pNext != NULL){(*pHead) = (*pHead)->m_pNext;}(*pHead)->m_pNext = pNode;(*pHead) = pNode;}void PrintList(ListNode *pHead){while (pHead != NULL){cout<<pHead->m_nValue<<" ";pHead = pHead->m_pNext;}cout<<endl;}ListNode* Reverse(ListNode *pHead){if (pHead == NULL || pHead->m_pNext == NULL){return pHead;}ListNode *pPre = NULL;ListNode *pCurrent = pHead;ListNode *pPost = pHead->m_pNext;while (pCurrent->m_pNext != NULL){pCurrent->m_pNext = pPre;pPre = pCurrent;pCurrent = pPost;pPost = pPost->m_pNext;}pCurrent->m_pNext = pPre;return pCurrent;}ListNode* ReverseList(ListNode *pHead, int k){if (pHead==NULL || pHead->m_pNext==NULL){return pHead;}ListNode *pPre = NULL;ListNode *pCurrent = pHead;ListNode *pPost = pHead->m_pNext;ListNode *pStart = NULL;ListNode *pEnd = NULL;int n = 0;pEnd = pCurrent;pEnd->m_pNext = NULL;while (pPost != NULL){++n;if (n == (k+1)){pStart = pPre;pEnd->m_pNext = ReverseList(pCurrent, k);return pStart;}else{pCurrent->m_pNext = pPre;pPre = pCurrent;pCurrent = pPost;pPost = pPost->m_pNext;}}pCurrent->m_pNext = pPre;pStart = Reverse(pCurrent);return pStart;}int main(){ListNode *pHead = NULL;ListNode *head = NULL;int n;cout<<"输入链表中节点的个数 n："<<endl;cin>>n;cout<<"请输入n个整数值："<<endl;for (int i=0; i<n; ++i){int data;cin>>data;if (pHead == NULL){pHead = CreateList(data);head = pHead;}else{InsertNode(&pHead, data);}}int k;cout<<"请输入k:"<<endl;cin>>k;head = ReverseList(head, k);PrintList(head);system("pause");return 0;}