几道简单的面试题

#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
using namespace std ;
struct _link_node{
int data ;
struct _link_node *next ;
} ;
struct _link_node* create_linklist(int data[],int len){
assert(data!=NULL) ;
struct _link_node *pRoot = (struct _link_node*)malloc(sizeof(struct _link_node)) ;
//pRoot->next = NULL ;
struct _link_node *pTmp = pRoot ;
for(int i=0;i<len;i++){
pTmp->next=(struct _link_node*)malloc(sizeof(struct _link_node)) ;
pTmp->next->data = data[i] ;
pTmp = pTmp->next ;
}
pTmp->next = NULL ;
return pRoot ;
}
struct _link_node* print_link(struct _link_node* pRoot){
struct _link_node *pTmp = pRoot ;
while(pTmp->next!=NULL){
printf("%d,",pTmp->next->data) ;
pTmp=pTmp->next ;
}
}
struct _link_node* get_reverse_n(struct _link_node* pRoot,int n){
assert(pRoot!=NULL) ;
struct _link_node *pPre = pRoot ;
struct _link_node *pTail = pRoot ;
int cnt = 0 ;
/*使用两个指针，第一个指针比第一个指针先走n步，两个指针再一起移动，
当先走指针走向末尾时，另外一个指针所指向的位置就是倒数第n个*/
while(cnt<n){
if(pPre==NULL){
return NULL ;
}
cnt++ ;
pPre=pPre->next ;
}
while(pPre!=NULL&&pPre->next!=NULL){
pPre=pPre->next ;
pTail=pTail->next ;
}
return pTail->next ;
}
void PrintMeet(){
int hour=0 ;
int minutes=0 ;
for(int i=1;i<6;i++){//模拟时针每走一小时，角度是30度
hour+=30 ;
for(int j=0;j<60;j++){//模拟秒针走，一步角度为6；
minutes+=6 ;
if(minutes%360==hour){
printf("time=%d:%d\n",hour/30,minutes%360/6) ;
}
}
}
}

int binary_search(int array[],int low,int high,int target){
if(low>high||array[high]<target){//advance abort
return -1 ;
}
int mid = low+((high-low)>>1) ;
while(low<=high){
mid = low+((high-low)>>1) ;
if(array[mid]<target){
low = mid+1 ;
}else if(array[mid]>target){
high = mid-1 ;
}else{
return mid ;
}
}
return -1 ;
}
int binary_search1(int array[],int low,int high,int target){
if(low>high){
return -1 ;
}else{
int mid = low+((high-low)>>1) ;
if(array[mid]>target){
high = mid-1 ;
binary_search1(array,low,high,target) ;
}else if(array[mid]<target){
low = mid + 1 ;
binary_search1(array,low,high,target) ;
}else{
return mid ;
}
}
}
int binary_find_upper_bound(int array[],int low,int high,int target){
if(low>high||array[high]<target){//advance abort
return -1 ;
}
int mid =low + ((high-low)>>1) ;
while(low<high){

if(array[mid]>target){
high = mid ;
}else{
low = mid+1 ;
}
mid = low+((high-low)>>1) ;
}
return array[mid] ;
}
int binary_find_lower_bound(int array[],int low,int high,int target){
if(low>high||array[high]<target){//advance abort
return -1 ;
}
int mid = low+((high-low)>>1) ;
while(low<high){
if(array[mid]<target){
low = mid ;
}else{
high=mid-1 ;
}
mid = low + ((high-low+1)>>1) ;//note:here we must add 1 to compute mid
}
return array[mid] ;
}
int find_first_cross_node(struct _link_node*pFirst, struct _link_node *pSecond){
assert(pFirst!=NULL&&pSecond!=NULL) ;
int len_first=0 ;
int len_second=0 ;
struct _link_node *pTmp1=pFirst ;
struct _link_node *pTmp2=pSecond ;

//first compute length of the two link list
while(pTmp1->next!=NULL){
pTmp1=pTmp1->next ;
len_first++ ;
}
while(pTmp2->next!=NULL){
pTmp2=pTmp2->next ;
len_second++ ;
}

// if not have cross ,return -1
if(pTmp1!=pTmp2){//if not cross
return -1 ;
}

//compare length of the two link list and difference of two link list length,
//and decide which list should move first
int b_first_long=len_first>len_second ;
int diff=b_first_long?(len_first-len_second):(len_second-len_first) ;

//the longer list should move diff steps
if(b_first_long){
pTmp1= pFirst ;
while(diff--){
pTmp1=pTmp1->next ;
printf("%d+",diff) ;
}
pTmp2 = pSecond ;
}else{
pTmp2=pSecond ;
while(diff--){
pTmp2=pTmp2->next ;
}
pTmp1 = pFirst ;
}

//compute the last positon and the position = diff + last move
int location=b_first_long?(len_first-len_second):(len_second-len_first) ;

while(pTmp1!=pTmp2) {
pTmp1=pTmp1->next ;
pTmp2=pTmp2->next ;
location++ ;
}
return location ;
}
void create_cross_linklist(struct _link_node* pFirst, struct _link_node *pSecond,int len1,int len2,int position){
assert(pFirst!=NULL&&pSecond!=NULL) ;
struct _link_node *pTmp1 = pFirst ;
struct _link_node *pTmp2 = pSecond ;
int cnt = 0;
if(len1>len2){
assert((len2+position)<len1) ;
while(cnt<len2){
pTmp1 = pTmp1->next ;
pTmp2 = pTmp2->next ;
cnt++ ;
}
cnt=0;
while(cnt<position){
pTmp1=pTmp1->next ;
cnt++ ;
}
pTmp2->next = pTmp1 ;
}else{
assert((len1+position)<len2) ;
while(cnt<len1){
pTmp1 = pTmp1->next ;
pTmp2 = pTmp2->next ;
cnt++ ;
}
cnt=0 ;
while(cnt<position){
pTmp2 = pTmp2->next ;
cnt++ ;
}
pTmp1->next = pTmp2 ;
}
}
int main()
{
int array[]={1,2,3,4,5,6,7,8,9,10,11,12,13,24} ;
int array1[]={2,3,4,6,1,3} ;
int len = sizeof(array)/sizeof(array[0]) ;
int len1 = sizeof(array1)/sizeof(array1[0]) ;

struct _link_node *pRoot1 = create_linklist(array,len) ;
struct _link_node *pRoot2 = create_linklist(array1,len1) ;
create_cross_linklist(pRoot1,pRoot2,len,len1,2) ;
printf("find first cross_node begin............\n") ;
printf("len=%d,len1=%d\n",len,len1) ;
int location = find_first_cross_node(pRoot1,pRoot2) ;
printf("first cross node at %d position\n",location) ;
printf("find first cross_node end............\n\n") ;

printf("binary search bound begin..........\n") ;
printf("location=%d\n",binary_search1(array,0,len-1,24)) ;
printf("upperbound=%d\n",binary_find_upper_bound(array,0,len-1,9)) ;
printf("lowerbound=%d\n",binary_find_lower_bound(array,0,len-1,9)) ;
printf("binary search bound end..........\n\n") ;

printf("find reciprocal n node begin..........\n") ;
struct _link_node *pRoot=create_linklist(array,len) ;
struct _link_node *pTmp=get_reverse_n(pRoot,3) ;
printf("data=%d\n",pTmp->data) ;
printf("find reciprocal n node end..........\n") ;
}