按降序显示列表

时间：2017-10-06 22:41:00

标签： c list

我有这个程序不会抛出错误，但是viewl程序只显示列表中的第一项。我如何为viewl程序打印但与程序查看器的顺序相反？

#include <stdio.h>
#include <conio.h>
#include <windows.h>
#include <stdlib.h>

struct list
{
    int info;
    struct list *nxt,*prv;
}*HEAD=NULL,*AUX=NULL,*P=NULL,*F=NULL,*QD=NULL,*FD=NULL;

主要功能（ok）

int main()
{
    void insertr(void);
    void extractr(void); 
    void viewr(void); 
    void viewl(void); 
    void deleten();
    void deletep();
    char opc;
    do
    {
        system("cls");
        printf("___________________________________________________\n");
        printf("_______¡¡¡DOUBLE-LINKED CIRCULAR LIST MENU!!!______\n");
        printf("___________________________________________________\n");
        printf("_________________SELECT AN OPTION__________________\n");
        printf("___________________________________________________\n");
        printf("___________________________________________________\n");
        printf("__________1) INSERT________________________________\n");
        printf("__________2) VIEW ASCENDING________________________\n");
        printf("__________3) VIEW DESCENDING_______________________\n");
        printf("__________4) ENTERING AND ELIMINATE NEXT___________\n");
        printf("__________5) ENTERING AND ELIMINATE PREVIOUS_______\n");
        printf("__________6) EXIT__________________________________\n");
        printf("___________________________________________________\n");
        opc=getch();
        switch(opc)
        {
        case '1':
            insertr();
            break;
        case '2':
            viewr();
            break;
        case '3':
            viewl();
            break;
        case '4':
            deleten();
            break;
        case '5':
            deletep();
            break;
        }
    }
    while(opc!='6');
    getch();
    return 0;
}

插入正确的流程

void insertr(void)
{
    P=HEAD;/* very first execution of this method P=NULL */
    AUX=(struct list *)malloc(sizeof(struct list));
    system("cls");
    printf("ENTER AN ENTIRE NUMBER: ");
    scanf("%d",&AUX->info);
    AUX->nxt=HEAD;
    AUX->prv=HEAD;
    F=AUX;
    if(HEAD==NULL)
    {
        HEAD=AUX;
        P = AUX;/*first execution of this method P is no longer NULL but P is pointing to AUX */
    }
    else
    {
        while (P->nxt!=HEAD)
        {
            P=P->nxt;
        }
    }
    P->nxt=AUX;
    AUX->prv=P;
    HEAD->prv=AUX;
}


void deleten()
{
    int x;
    system("cls");
    printf("ENTER A NUMBER TO ELIMINATE THE FOLLOWING: ");
    scanf("%d",&x);

    FD=HEAD;
    QD=HEAD;
    while(FD->info!=x&&FD->nxt!=HEAD)
    {
        FD=FD->nxt;
    }
    QD=FD->nxt;

    if(FD->nxt==HEAD&&FD->info!=x)
    {
        printf("\nENTERED NUMBER IS NOT LISTED");
    }
    else
    {
        if(FD->info==x)
        {
            FD->nxt=QD->nxt;
            (QD->nxt)->prv=FD;
            printf("\nDELETED %d",QD->info);
            free(QD);
        }
    }
    getch();
}

deletea process（ok）

void deletep()
{
    int x;
    system("cls");
    printf("ENTER A NUMBER TO REMOVE THE PREVIOUS ");
    scanf("%d",&x);

    FD=HEAD;
    QD=HEAD;
    while (FD->info!=x&&FD->nxt!=HEAD)
    {
        FD=FD->nxt;
    }
    QD=FD->prv;
    if(FD->nxt==HEAD&&FD->info!=x)
    {
        printf("\nENTERED NUMBER IS NOT LISTED");
    }
    else
    {
        if(FD->info==x)
        {
            FD->prv=QD->prv;
            (QD->prv)->nxt=FD;
            printf("\nDELETED %d",QD->info);
            free(QD);
        }
    }
    getch();
}

查看过程（确定）：

void viewr(void)
{
    system("cls");
    if(HEAD==NULL)
    {
        printf("EMPTY LIST");
        getchar();
        return;
    }
    AUX=HEAD;
    printf("LIST:\n\n");
    while(AUX->nxt!=HEAD)
    {
        printf("-> %d\n",AUX->info);
        AUX=AUX->nxt;
    }
    if(AUX->nxt==HEAD)
    {
        printf("-> %d\n",AUX->info);
    }
    getch();
}

此功能失败：

void viewl(void)
{
    system("cls");
    if(HEAD==NULL)
    {
        printf("EMPTY LIST");
        getchar();
        return;
    }
    AUX=F;
    printf("LIST:\n\n");
    do
    {
        printf("-> %d\n",AUX->info);
        AUX=AUX->prv;
    }
    while(AUX->nxt!=HEAD);
    getch();
}

2 个答案:

答案 0 :(得分：0)

你的代码中的

：

do
{
    printf("-> %d\n",AUX->info);
    AUX=AUX->prv;
}
while(AUX->nxt!=HEAD);

可能会发生这样的事情。

enter image description here

当您前往上一个节点并检查next是否为head时，如果您将列表构建为双链接和循环，则next将成为head。

尝试这样：

do
{
    AUX=AUX->prv;
    printf("-> %d\n",AUX->info);
}
while(AUX!=HEAD);

并且您应该避免将所有变量用作全局变量。

答案 1 :(得分：0)

代码有几个逻辑错误，其他变量等。这里没有问题

#include<stdio.h>
#include<stdlib.h>
#include<conio.h>
#include<windows.h>

//THIS IS TO CREATE THE LIST

struct list{
    int info; 
    struct list *nxt,*prv;
}*HEAD=NULL,*AUX=NULL,*P=NULL,*FD=NULL,*QD=NULL,*Fd=NULL,*Qd=NULL;

int main(){  
    void insertr(void);
    void viewr(void); 
    void viewl(void); 
    void deleten();
    void deletep();
    char opt; 
    do{  
        system("cls");  

        printf("___________________________________________________\n");
        printf("_______¡¡¡DOUBLE-LINKED CIRCULAR LIST MENU!!!______\n");
        printf("___________________________________________________\n");
        printf("_________________SELECT AN OPTION__________________\n");
        printf("___________________________________________________\n");
        printf("___________________________________________________\n");
        printf("__________1) INSERT________________________________\n");
        printf("__________2) VIEW ASCENDING________________________\n");
        printf("__________3) VIEW DESCENDING_______________________\n");
        printf("__________4) ENTERING AND ELIMINATE NEXT___________\n");
        printf("__________5) ENTERING AND ELIMINATE PREVIOUS_______\n");
        printf("__________6) EXIT__________________________________\n");
        printf("___________________________________________________\n");
        opt=getch();
        switch(opt)  {    
        case '1':  
            insertr();   
            break;    
        case '2': 
            viewr();  
            break;   
        case '3': 
            viewl();
            break;
        case '4':
            deleten(); 
            break;  
            case'5': 
                deletep();  
                break;
        }  
    }while(opt!='6'); 
    return 0;
}

void insertr(void){
    P=HEAD; /* very first execution of this method P=NULL */
    AUX=(struct list *)malloc(sizeof(struct list)); 
    system("cls");
    printf("ENTER AN ENTIRE NUMBER: "); 
    scanf("%d",&AUX->info);
    AUX->nxt=HEAD;
    AUX->prv=HEAD; // The pointer to the previous node is null (HEAD is null)
    if(HEAD==NULL){ //I ask if HEAD is equal to Null
        HEAD=AUX;
        P=AUX; /* The first execution of this method P is no longer NULL but P is pointing to AUX */
    }else{ //THIS YES  
        while(P->nxt!=HEAD){  
            P=P->nxt; 
        }
    }
    P->nxt=AUX; // The next pointer of P takes the value of AUX
    AUX->prv=P;
    HEAD->prv=AUX;
}

void deleten(){
    int x;
    system("cls");
    printf("ENTER A NUMBER TO ELIMINATE THE FOLLOWING: ");
    scanf("%d",&x);
    FD=HEAD;
    QD=HEAD;
    while(FD->info!=x&&FD->nxt!=HEAD){ // if what I am going to eliminate is different from the number that was entered and if there is another
        FD=FD->nxt; //step to the next node
    }
    QD=FD->nxt;
    if(FD->nxt==HEAD&&FD->info==x){
        printf("\nIT IS THE HEADBOARD! CAN NOT BE ELIMINATED");
    }else
       if(FD->nxt==HEAD&&FD->info!=x){
        printf("\nTHE NUMBER ENTERED IS NOT IN THE LIST");
    }else{
           FD->nxt=QD->nxt;
           (QD->nxt)->prv=FD;
           printf("\nDELETED %d",QD->info);
           free(QD); //free space in memory occupied by QD
       }
       getch();
}

void deletep()
{
    int xd;
    system("cls");
    printf("IENTER A NUMBER TO REMOVE THE PREVIOUS: ");
    scanf("%d",&xd);

    Fd=HEAD;
    Qd=HEAD;
    while(Fd->info!=xd){
        Fd=Fd->prv;
    } Qd=Fd->prv;

    if(Fd==HEAD){
        printf("\nIT'S THE HEAD! CAN NOT BE ELIMINATED");
    }else{
        if(Qd==HEAD){
            HEAD=HEAD->nxt;
            Fd->prv=Qd->prv;
            (Fd->prv)->nxt=Fd;
            printf("\nDELETED %d",Qd->info);
        }else{
            Fd->prv=Qd->prv;
            (Qd->prv)->nxt=Fd;
            printf("\nDELETED %d",Qd->info);
        }
        free(Qd);
    }
    getch();
}

void viewr(void)
{
    system("cls");
    if(HEAD==NULL){
        printf("LISTA VACIA");
        getchar();
        return;
    }
    AUX=HEAD;
    printf("LISTA:\n\n");
    while(AUX->nxt!=HEAD){
        printf("->%d\n",AUX->info);
        AUX=AUX->nxt;
    }
    if(AUX->nxt==HEAD){
        printf("->%d\n",AUX->info);
    }
    getch();
}

void viewl(void){
    system("cls"); 
    if(HEAD==NULL){ 
        printf("EMPTY LIST");
        getchar();  
        return; 
    } AUX=HEAD->prv; 
    printf("LIST:\n\n");
    do{  
        printf("->%d\n",AUX->info); 
        AUX=AUX->prv; 
    }while(AUX->nxt!=HEAD);
    getch();
}
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