最近找工作突然冒出来两个疑问

[ruifengzhangyi9999]

1 二叉树在什么场合使用，除了可以排序还有呢，查询快 但是哈希表也查询快啊
2 生产者 消费者模型什么场合使用，是不是服务端都可以用这个

[勤奋的小游侠]

二叉树可以保证最怀的情况下的插入时间复杂度为logn，哈希表应该做不到。哈希表有键值是有限的，假如所有的数据哈希值都相同，会挂在同一个节点上，哈希值就完全没有意义了，只能按插入顺序遍历挂在该节点所有值。平衡二叉树就不存在这样的问题

[ruifengzhangyi9999]

多谢楼上 我接触过的系统中有同时使用树和哈希表的 我的理解当数量特别庞大，需要快速查询就用哈希表 当匹配有多个项目时 比如范围 不能用key区分 就使用树

[赵4老师]

#include <iostream>
#include <stack>
#include <queue>
#include <locale.h>
using namespace std;
typedef struct BiTNode {//二叉树结点
    char data;                      //数据
    struct BiTNode *lchild,*rchild; //左右孩子指针
} BiTNode,*BiTree;
int CreateBiTree(BiTree &T) {//按先序序列创建二叉树
    char data;
    scanf("%c",&data);//按先序次序输入二叉树中结点的值（一个字符），‘#’表示空树
    if (data == '#') {
        T = NULL;
    } else {
        T = (BiTree)malloc(sizeof(BiTNode));
        T->data = data;         //生成根结点
        CreateBiTree(T->lchild);//构造左子树
        CreateBiTree(T->rchild);//构造右子树
    }
    return 0;
}
void Visit(BiTree T) {//输出
    if (T->data != '#') {
        printf("%c ",T->data);
    }
}
void PreOrder(BiTree T) {//先序遍历
    if (T != NULL) {
        Visit(T);               //访问根节点
        PreOrder(T->lchild);    //访问左子结点
        PreOrder(T->rchild);    //访问右子结点
    }
}
void InOrder(BiTree T) {//中序遍历
    if (T != NULL) {
        InOrder(T->lchild);     //访问左子结点
        Visit(T);               //访问根节点
        InOrder(T->rchild);     //访问右子结点
    }
}
void PostOrder(BiTree T) {//后序遍历
    if (T != NULL) {
        PostOrder(T->lchild);   //访问左子结点
        PostOrder(T->rchild);   //访问右子结点
        Visit(T);               //访问根节点
    }
}
void PreOrder2(BiTree T) {//先序遍历(非递归)
//访问T->data后，将T入栈，遍历左子树；遍历完左子树返回时，栈顶元素应为T，出栈，再先序遍历T的右子树。
    stack<BiTree> stack;
    BiTree p = T;//p是遍历指针
    while (p || !stack.empty()) {   //栈不空或者p不空时循环
        if (p != NULL) {
            stack.push(p);          //存入栈中
            printf("%c ",p->data);  //访问根节点
            p = p->lchild;          //遍历左子树
        } else {
            p = stack.top();        //退栈
            stack.pop();
            p = p->rchild;          //访问右子树
        }
    }
}
void InOrder2(BiTree T) {//中序遍历(非递归)
//T是要遍历树的根指针，中序遍历要求在遍历完左子树后，访问根，再遍历右子树。
//先将T入栈，遍历左子树；遍历完左子树返回时，栈顶元素应为T，出栈，访问T->data，再中序遍历T的右子树。
    stack<BiTree> stack;
    BiTree p = T;//p是遍历指针
    while (p || !stack.empty()) {   //栈不空或者p不空时循环
        if (p != NULL) {
            stack.push(p);          //存入栈中
            p = p->lchild;          //遍历左子树
        } else {
            p = stack.top();        //退栈，访问根节点
            printf("%c ",p->data);
            stack.pop();
            p = p->rchild;          //访问右子树
        }
    }
}

typedef struct BiTNodePost{
    BiTree biTree;
    char tag;
} BiTNodePost,*BiTreePost;
void PostOrder2(BiTree T) {//后序遍历(非递归)
    stack<BiTreePost> stack;
    BiTree p = T;//p是遍历指针
    BiTreePost BT;
    while (p != NULL || !stack.empty()) {//栈不空或者p不空时循环
        while (p != NULL) {//遍历左子树
            BT = (BiTreePost)malloc(sizeof(BiTNodePost));
            BT->biTree = p;
            BT->tag = 'L';//访问过左子树
            stack.push(BT);
            p = p->lchild;
        }
        while (!stack.empty() && (stack.top())->tag == 'R') {//左右子树访问完毕访问根节点
            BT = stack.top();
            stack.pop();//退栈
            printf("%c ",BT->biTree->data);
        }
        if (!stack.empty()) {//遍历右子树
            BT = stack.top();
            BT->tag = 'R';//访问过右子树
            p = BT->biTree;
            p = p->rchild;
        }
    }
}

void LevelOrder(BiTree T) {//层次遍历
    if (T == NULL) return;
    BiTree p = T;
    queue<BiTree> queue;//队列
    queue.push(p);//根节点入队
    while (!queue.empty()) {    //队列不空循环
        p = queue.front();      //对头元素出队
        printf("%c ",p->data);  //访问p指向的结点
        queue.pop();            //退出队列
        if (p->lchild != NULL) {//左子树不空，将左子树入队
            queue.push(p->lchild);
        }
        if (p->rchild != NULL) {//右子树不空，将右子树入队
            queue.push(p->rchild);
        }
    }
}
int main() {
    BiTree T;

    setlocale(LC_ALL,"chs");
    CreateBiTree(T);

    printf("先序遍历        ：");PreOrder  (T);printf("\n");
    printf("先序遍历(非递归)：");PreOrder2 (T);printf("\n");
                                               printf("\n");
    printf("中序遍历        ：");InOrder   (T);printf("\n");
    printf("中序遍历(非递归)：");InOrder2  (T);printf("\n");
                                               printf("\n");
    printf("后序遍历        ：");PostOrder (T);printf("\n");
    printf("后序遍历(非递归)：");PostOrder2(T);printf("\n");
                                               printf("\n");
    printf("层次遍历        ：");LevelOrder(T);printf("\n");

    return 0;
}
//ABC##DE#G##F###
//先序遍历        ：A B C D E G F
//先序遍历(非递归)：A B C D E G F
//
//中序遍历        ：C B E G D F A
//中序遍历(非递归)：C B E G D F A
//
//后序遍历        ：C G E F D B A
//后序遍历(非递归)：C G E F D B A
//
//层次遍历        ：A B C D E F G
//

///       A
///      /
///     B
///    / \
///   C   D
///      / \
///     E   F
///      \
///       G

[赵4老师]

//循环向a函数每次发送200个字节长度（这个是固定的）的buffer,
//a函数中需要将循环传进来的buffer，组成240字节（也是固定的）的新buffer进行处理，
//在处理的时候每次从新buffer中取两个字节打印
#ifdef WIN32
    #pragma warning(disable:4996)
#endif
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#ifdef WIN32
    #include <windows.h>
    #include <process.h>
    #include <io.h>
    #define  MYVOID             void
    #define  vsnprintf          _vsnprintf
#else
    #include <unistd.h>
    #include <sys/time.h>
    #include <pthread.h>
    #define  CRITICAL_SECTION   pthread_mutex_t
    #define  MYVOID             void *
#endif
//Log{
#define MAXLOGSIZE 20000000
#define MAXLINSIZE 16000
#include <time.h>
#include <sys/timeb.h>
#include <stdarg.h>
char logfilename1[]="MyLog1.log";
char logfilename2[]="MyLog2.log";
static char logstr[MAXLINSIZE+1];
char datestr[16];
char timestr[16];
char mss[4];
CRITICAL_SECTION cs_log;
FILE *flog;
#ifdef WIN32
void Lock(CRITICAL_SECTION *l) {
    EnterCriticalSection(l);
}
void Unlock(CRITICAL_SECTION *l) {
    LeaveCriticalSection(l);
}
void sleep_ms(int ms) {
    Sleep(ms);
}
#else
void Lock(CRITICAL_SECTION *l) {
    pthread_mutex_lock(l);
}
void Unlock(CRITICAL_SECTION *l) {
    pthread_mutex_unlock(l);
}
void sleep_ms(int ms) {
    usleep(ms*1000);
}
#endif
void LogV(const char *pszFmt,va_list argp) {
    struct tm *now;
    struct timeb tb;

    if (NULL==pszFmt||0==pszFmt[0]) return;
    vsnprintf(logstr,MAXLINSIZE,pszFmt,argp);
    ftime(&tb);
    now=localtime(&tb.time);
    sprintf(datestr,"%04d-%02d-%02d",now->tm_year+1900,now->tm_mon+1,now->tm_mday);
    sprintf(timestr,"%02d:%02d:%02d",now->tm_hour     ,now->tm_min  ,now->tm_sec );
    sprintf(mss,"%03d",tb.millitm);
    printf("%s %s.%s %s",datestr,timestr,mss,logstr);
    flog=fopen(logfilename1,"a");
    if (NULL!=flog) {
        fprintf(flog,"%s %s.%s %s",datestr,timestr,mss,logstr);
        if (ftell(flog)>MAXLOGSIZE) {
            fclose(flog);
            if (rename(logfilename1,logfilename2)) {
                remove(logfilename2);
                rename(logfilename1,logfilename2);
            }
        } else {
            fclose(flog);
        }
    }
}
void Log(const char *pszFmt,...) {
    va_list argp;

    Lock(&cs_log);
    va_start(argp,pszFmt);
    LogV(pszFmt,argp);
    va_end(argp);
    Unlock(&cs_log);
}
//Log}
#define ASIZE    200
#define BSIZE    240
#define CSIZE      2
char Abuf[ASIZE];
char Cbuf[CSIZE];
CRITICAL_SECTION cs_HEX ;
CRITICAL_SECTION cs_BBB ;
struct FIFO_BUFFER {
    int  head;
    int  tail;
    int  size;
    char data[BSIZE];
} BBB;
int No_Loop=0;
void HexDump(int cn,char *buf,int len) {
    int i,j,k;
    char binstr[80];

    Lock(&cs_HEX);
    for (i=0;i<len;i++) {
        if (0==(i%16)) {
            sprintf(binstr,"%03d %04x -",cn,i);
            sprintf(binstr,"%s %02x",binstr,(unsigned char)buf[i]);
        } else if (15==(i%16)) {
            sprintf(binstr,"%s %02x",binstr,(unsigned char)buf[i]);
            sprintf(binstr,"%s  ",binstr);
            for (j=i-15;j<=i;j++) {
                sprintf(binstr,"%s%c",binstr,('!'<buf[j]&&buf[j]<='~')?buf[j]:'.');
            }
            Log("%s\n",binstr);
        } else {
            sprintf(binstr,"%s %02x",binstr,(unsigned char)buf[i]);
        }
    }
    if (0!=(i%16)) {
        k=16-(i%16);
        for (j=0;j<k;j++) {
            sprintf(binstr,"%s   ",binstr);
        }
        sprintf(binstr,"%s  ",binstr);
        k=16-k;
        for (j=i-k;j<i;j++) {
            sprintf(binstr,"%s%c",binstr,('!'<buf[j]&&buf[j]<='~')?buf[j]:'.');
        }
        Log("%s\n",binstr);
    }
    Unlock(&cs_HEX);
}
int GetFromRBuf(int cn,CRITICAL_SECTION *cs,FIFO_BUFFER *fbuf,char *buf,int len) {
    int lent,len1,len2;

    lent=0;
    Lock(cs);
    if (fbuf->size>=len) {
        lent=len;
        if (fbuf->head+lent>BSIZE) {
            len1=BSIZE-fbuf->head;
            memcpy(buf     ,fbuf->data+fbuf->head,len1);
            len2=lent-len1;
            memcpy(buf+len1,fbuf->data           ,len2);
            fbuf->head=len2;
        } else {
            memcpy(buf     ,fbuf->data+fbuf->head,lent);
            fbuf->head+=lent;
        }
        fbuf->size-=lent;
    }
    Unlock(cs);
    return lent;
}
MYVOID thdB(void *pcn) {
    char        *recv_buf;
    int          recv_nbytes;
    int          cn;
    int          wc;
    int          pb;

    cn=(int)pcn;
    Log("%03d thdB              thread begin...\n",cn);
    while (1) {
        sleep_ms(10);
        recv_buf=(char *)Cbuf;
        recv_nbytes=CSIZE;
        wc=0;
        while (1) {
            pb=GetFromRBuf(cn,&cs_BBB,&BBB,recv_buf,recv_nbytes);
            if (pb) {
                Log("%03d recv %d bytes\n",cn,pb);
                HexDump(cn,recv_buf,pb);
                sleep_ms(1);
            } else {
                sleep_ms(1000);
            }
            if (No_Loop) break;//
            wc++;
            if (wc>3600) Log("%03d %d==wc>3600!\n",cn,wc);
        }
        if (No_Loop) break;//
    }
#ifndef WIN32
    pthread_exit(NULL);
#endif
}
int PutToRBuf(int cn,CRITICAL_SECTION *cs,FIFO_BUFFER *fbuf,char *buf,int len) {
    int lent,len1,len2;

    Lock(cs);
    lent=len;
    if (fbuf->size+lent>BSIZE) {
        lent=BSIZE-fbuf->size;
    }
    if (fbuf->tail+lent>BSIZE) {
        len1=BSIZE-fbuf->tail;
        memcpy(fbuf->data+fbuf->tail,buf     ,len1);
        len2=lent-len1;
        memcpy(fbuf->data           ,buf+len1,len2);
        fbuf->tail=len2;
    } else {
        memcpy(fbuf->data+fbuf->tail,buf     ,lent);
        fbuf->tail+=lent;
    }
    fbuf->size+=lent;
    Unlock(cs);
    return lent;
}
MYVOID thdA(void *pcn) {
    char        *send_buf;
    int          send_nbytes;
    int          cn;
    int          wc;
    int           a;
    int          pa;

    cn=(int)pcn;
    Log("%03d thdA              thread begin...\n",cn);
    a=0;
    while (1) {
        sleep_ms(100);
        memset(Abuf,a,ASIZE);
        a=(a+1)%256;
        if (16==a) {No_Loop=1;break;}//去掉这句可以让程序一直循环直到按Ctrl+C或Ctrl+Break或当前目录下存在文件No_Loop
        send_buf=(char *)Abuf;
        send_nbytes=ASIZE;
        Log("%03d sending %d bytes\n",cn,send_nbytes);
        HexDump(cn,send_buf,send_nbytes);
        wc=0;
        while (1) {
            pa=PutToRBuf(cn,&cs_BBB,&BBB,send_buf,send_nbytes);
            Log("%03d sent %d bytes\n",cn,pa);
            HexDump(cn,send_buf,pa);
            send_buf+=pa;
            send_nbytes-=pa;
            if (send_nbytes<=0) break;//
            sleep_ms(1000);
            if (No_Loop) break;//
            wc++;
            if (wc>3600) Log("%03d %d==wc>3600!\n",cn,wc);
        }
        if (No_Loop) break;//
    }
#ifndef WIN32
    pthread_exit(NULL);
#endif
}
int main() {
#ifdef WIN32
    InitializeCriticalSection(&cs_log);
    InitializeCriticalSection(&cs_HEX );
    InitializeCriticalSection(&cs_BBB );
#else
    pthread_t threads[2];
    int threadsN;
    int rc;
    pthread_mutex_init(&cs_log,NULL);
    pthread_mutex_init(&cs_HEX,NULL);
    pthread_mutex_init(&cs_BBB,NULL);
#endif
    Log("Start===========================================================\n");

    BBB.head=0;
    BBB.tail=0;
    BBB.size=0;

#ifdef WIN32
    _beginthread((void(__cdecl *)(void *))thdA,0,(void *)1);
    _beginthread((void(__cdecl *)(void *))thdB,0,(void *)2);
#else
    threadsN=0;
    rc=pthread_create(&(threads[threadsN++]),NULL,thdA,(void *)1);if (rc) Log("%d=pthread_create %d error!\n",rc,threadsN-1);
    rc=pthread_create(&(threads[threadsN++]),NULL,thdB,(void *)2);if (rc) Log("%d=pthread_create %d error!\n",rc,threadsN-1);
#endif

    if (!access("No_Loop",0)) {
        remove("No_Loop");
        if (!access("No_Loop",0)) {
            No_Loop=1;
        }
    }
    while (1) {
        sleep_ms(1000);
        if (No_Loop) break;//
        if (!access("No_Loop",0)) {
            No_Loop=1;
        }
    }
    sleep_ms(3000);
    Log("End=============================================================\n");
#ifdef WIN32
    DeleteCriticalSection(&cs_BBB );
    DeleteCriticalSection(&cs_HEX );
    DeleteCriticalSection(&cs_log);
#else
    pthread_mutex_destroy(&cs_BBB);
    pthread_mutex_destroy(&cs_HEX);
    pthread_mutex_destroy(&cs_log);
#endif
    return 0;
}

[反转灵魂]

数据结构不是说让你一遇到问题就对号入座，哪个结构好哪个结构不行。