我在雙向鏈表中的交換代碼有問題

Question

我在 C 中制作了交換代碼，但我在學校編譯器中沒有獲得完美的成績。 我認為下面的代碼有問題。 我用結構和指針制作了雙向鏈表。 節點定義為：

struct node* newnode(char x)
{
    struct node* new = (struct node*)malloc(sizeof(struct node));
    new->next = NULL;
    new->prev = NULL;
    new->c = x;

    return new;
}

下面的代碼是交換代碼，我使每個 function 因子意味着“struct node*p”是從頭到尾的完整列表，“int a and b”是列表的排名，“count1(p)”是 function完整列表中的節點並返回節點數（不包括頭部和尾部）。

void swap(struct node* p, int a, int b)
{
    int x, y; 
    struct node* x1, * x2, emp = { 0 };
    int i = 0;
    x1 = p;
    x2 = p;

    if (a >= b) {
        x = b;
        y = a;
    }
    else {
        x = a;
        y = b;
    }
if (b <= 0 || a <= 0 || a > N || a > count1(p) || b > N || b > count1(p)) {
        printf("invalid position\n");
        return;
    }while (i < x && x1 != tail) {
        x1 = x1->next;
        i++;
    }
    i = 0;
    while (i < y && p != tail) {
        x2 = x2->next;
        i++;
    }
    if (x1->next != x2)
    {
        x1->prev->next = x2;
        x1->next->prev = x2;
        x2->prev->next = x1;
        x2->next->prev = x1;
        emp.next = x1->next;
        emp.prev = x1->prev;
        x1->next = x2->next;
        x1->prev = x2->prev;
        x2->next = emp.next;
        x2->prev = emp.prev;
    }
    if (x1->next == x2)
    {
        emp.prev = x1->prev;
        emp.next = x1->next;
        x1->prev->next = x2;
        x2->next->prev = x1;
        x1->prev = x2;
        x1->next = x2->next;
        x2->prev = emp.prev;
        x2->next = x1;


    }

}

以下代碼是我的完整代碼：

#include<stdio.h>
#include<stdlib.h>
int N;
struct node {
    struct node* next;
    struct node* prev;
    char c;
};
struct node* head, * tail;

void reset() {

    head = (struct node*)malloc(sizeof(struct node));
    tail = (struct node*)malloc(sizeof(struct node));
    head->prev = NULL;
    head->next = tail;
    head->c = NULL;
    tail->prev = head;
    tail->next = NULL;
    tail->c = NULL;
}
struct node* newnode(char x)
{
    struct node* new = (struct node*)malloc(sizeof(struct node));
    new->next = NULL;
    new->prev = NULL;
    new->c = x;

    return new;
}
void prcount(struct node* p)
{

    printf("%d\n", count1(p));
}
int count1(struct node* p)
{
    int sum = 0;

    while (p != tail) {
        p = p->next;

        sum++;

    }
    return sum + -1;
}
void add1(struct node* p, int n, char x)
{
    struct node* new1 = newnode(x);
    int i = 1;
    if (n <= 0 || n > N || n > count1(p) + 1) {
        printf("invalid position\n");
        return;
    }
    while (i < n && p != tail) {
        p = p->next;

        i++;

    }
    p->next->prev = new1;
    new1->prev = p;
    new1->next = p->next;
    p->next = new1;

}
void delete1(struct node* p, int n)
{
    int i = 0;
    if (n <= 0 || n > N || n > count1(p)) {
        printf("invalid position\n");
        return;
    }
    while (i < n && p != tail)
    {
        p = p->next;
        i++;
    }
    p->prev->next = p->next;
    p->next->prev = p->prev;
    free(p);


}
void get1(struct node* p, int n) {
    int i = 0;
    if (n <= 0 || n > N || n > count1(p)) {
        printf("invalid position\n");
        return;
    }while (i < n && p != tail) {
        p = p->next;
        i++;
    }
    printf("%c\n", p->c);
}
void print1(struct node* p)
{
    int i = 0;
    if (count1(p) == 0) {
        printf("invalid position\n");
        return;
    }
    while (i < N && p->next != tail)
    {
        p = p->next;
        printf("%c", p->c);
        i++;
    }
    printf("\n");

}void removeall(struct node* p)
{

    struct node* emp;
    p = p->next;


    while (p != tail)

    {
        emp = p->next;
        free(p);
        p = emp;
    }
    head->prev = NULL;
    head->next = tail;
    head->c = NULL;
    tail->prev = head;
    tail->next = NULL;
    tail->c = NULL;
}
void swap(struct node* p, int a, int b)
{
    int x, y;
    struct node* x1, * x2, emp = { 0 };
    int i = 0;
    x1 = p;
    x2 = p;

    if (a >= b) {
        x = b;
        y = a;
    }
    else {
        x = a;
        y = b;
    }

    if (b <= 0 || a <= 0 || a > N || a > count1(p) || b > N || b > count1(p)) {
        printf("invalid position\n");
        return;
    }while (i < x && x1 != tail) {
        x1 = x1->next;
        i++;
    }
    i = 0;
    while (i < y && x2 != tail) {
        x2 = x2->next;
        i++;
    }
    if (x1->next != x2)
    {
        x1->prev->next = x2;
        x1->next->prev = x2;
        x2->prev->next = x1;
        x2->next->prev = x1;
        emp.next = x1->next;
        emp.prev = x1->prev;
        x1->next = x2->next;
        x1->prev = x2->prev;
        x2->next = emp.next;
        x2->prev = emp.prev;
    }
    if (x1->next == x2)
    {
        emp.prev = x1->prev;
        emp.next = x1->next;
        x1->prev->next = x2;
        x2->next->prev = x1;
        x1->prev = x2;
        x1->next = x2->next;
        x2->prev = emp.prev;
        x2->next = x1;


    }

}
int main()
{
    int i;
    int r, n;
    char x, y;

    reset();

    scanf("%d", &N);
    for (i = 0; i < N; i++)
    {
        scanf(" %c", &x);
        if (x == 'A') {//A mean add(head,int a, char x) -> add 'x' on a rank in list
            scanf("%d", &r);

            scanf(" %c", &y);

            add1(head, r, y);
        }
        else if (x == 'D') {// D mean delete(struct node *head, int a) -> delete element on int a rank
            scanf("%d", &r);

            delete1(head, r);
        }
        else if (x == 'G') {//G mean Get(head,int a)-> print element on int a rank
            scanf("%d", &r);
            get1(head, r);

        }
        else if (x == 'P') {//P mean print(head) -> print all element in list
            print1(head);
        }
        else if (x == 'R') {//R mean Removeall(head) -> remove all node (exclude head and tail0
            removeall(head);
        }
        else if (x == 'C')//C Mean prcount(head) -> count and print number of node in list (exclude head and tail)
        {
            prcount(head);
        }
        else if (x == 'S') {//S mean Swap(head, int a, int b) -> swap element of int a rank with int b rank 
            scanf("%d", &r);
            scanf("%d", &n);
            swap(head, r, n);
        }
    }
    removeall(head);
}

這是我的完整代碼。 我想知道制作交換代碼有什么問題或更有效的方法嗎？

Answer 1

#include<stdio.h>
#include<stdlib.h>
int N;
struct node {
    struct node* next;
    struct node* prev;
    char c;
};
struct node* head, * tail;

void reset() {

    head = (struct node*)malloc(sizeof(struct node));
    tail = (struct node*)malloc(sizeof(struct node));
    head->prev = NULL;
    head->next = tail;
    head->c = NULL;
    tail->prev = head;
    tail->next = NULL;
    tail->c = NULL;
}
struct node* newnode(char x)
{
    struct node* new = (struct node*)malloc(sizeof(struct node));
    new->next = NULL;
    new->prev = NULL;
    new->c = x;

    return new;
}
void prcount(struct node* p)
{
    
    printf("%d\n", count1(p));
}
int count1(struct node* p)
{
    int sum = 0;

    while (p != tail) {
        p = p->next;

        sum++;

    }
    return sum + -1;
}
void add1(struct node* p, int n, char x)
{
    struct node * new1 = newnode(x);
    int i = 1;
    if (n<=0||n > N || n > count1(p) + 1) {
        printf("invalid position\n");
        return;
    }
    while (i < n && p != tail) {
        p = p->next;

        i++;

    }
    p->next->prev = new1;
    new1->prev = p;
    new1->next = p->next;
    p->next = new1;

}
void delete1(struct node* p, int n)
{
    int i = 0;
    if (n <= 0 || n > N || n > count1(p)) {
        printf("invalid position\n");
        return;
    }
    while (i < n && p != tail)
    {
        p = p->next;
        i++;
    }
    p->prev->next = p->next;
    p->next->prev = p->prev;
    free(p);


}
void get1(struct node* p, int n) {
    int i = 0;
    if (n <= 0 || n > N || n > count1(p)) {
        printf("invalid position\n");
        return;
    }while (i < n && p != tail) {
        p = p->next;
        i++;
    }
    printf("%c\n", p->c);
}
void print1(struct node* p)
{
    int i = 0;
    if (count1(p) == 0) {
        printf("invalid position\n");
        return;
    }
    while (i < N && p->next != tail)
    {
        p = p->next;
        printf("%c", p->c);
        i++;
    }
    printf("\n");

}void removeall(struct node* p)
{

    struct node* emp;
    p = p->next;

    
    while (p != tail)

    {
        emp = p->next;
        free(p);
        p = emp;
    }
    head->prev = NULL;
    head->next = tail;
    head->c = NULL;
    tail->prev = head;
    tail->next = NULL;
    tail->c = NULL;
}
void swap(struct node* p, int a, int b)
{
    int x, y; 
    struct node* x1, * x2, emp = { 0 };
    int i = 0;
    x1 = p;
    x2 = p;

    if (a >= b) {
        x = b;
        y = a;
    }
    else {
        x = a;
        y = b;
    }
    
    if (b <= 0 || a <= 0 || a > N || a > count1(p) || b > N || b > count1(p)) {
        printf("invalid position\n");
        return;
    }while (i < x && x1 != tail) {
        x1 = x1->next;
        i++;
    }
    i = 0;
    while (i < y && p != tail) {
        x2 = x2->next;
        i++;
    }
    if (x1->next != x2)
    {
        x1->prev->next = x2;
        x1->next->prev = x2;
        x2->prev->next = x1;
        x2->next->prev = x1;
        emp.next = x1->next;
        emp.prev = x1->prev;
        x1->next = x2->next;
        x1->prev = x2->prev;
        x2->next = emp.next;
        x2->prev = emp.prev;
    }
    if (x1->next == x2)
    {
        emp.prev = x1->prev;
        emp.next = x1->next;
        x1->prev->next = x2;
        x2->next->prev = x1;
        x1->prev = x2;
        x1->next = x2->next;
        x2->prev = emp.prev;
        x2->next = x1;


    }

}
int main()
{
    int i;
    int r, n;
    char x, y;

    reset();

    scanf("%d", &N);
    for (i = 0; i < N; i++)
    {
        scanf(" %c", &x);
        if (x == 'A') {
            scanf("%d", &r);

            scanf(" %c", &y);

            add1(head, r, y);
        }
        else if (x == 'D') {
            scanf("%d", &r);

            delete1(head, r);
        }
        else if (x == 'G') {
            scanf("%d", &r);
            get1(head, r);

        }
        else if (x == 'P') {
            print1(head);
        }
        else if (x == 'R') {
            removeall(head);
        }
        else if (x == 'C')
        {
            prcount(head);
        }
        else if (x == 'S') {
            scanf("%d", &r);
            scanf("%d", &n);
            swap(head, r, n);
        }
    }
    removeall(head);
}

這是我的完整代碼

Answer 2

int N用作main中輸入命令的數量。 與列表函數中的N進行比較（好像N表示節點數）沒有任何意義 - 您可以直接刪除它們。

Besides that, there are some places where a compiler with appropriate options would issue warnings - perhaps that's why you didnt get perfect grade in school compiler .

     head->c = NULL;

由於c是char類型，而NULL是null 指針常量，因此不適合； 改成

     head->c = '\0';    // or head->c = 0;

---

     printf("%d\n", count1(p));

在聲明之前，您可以在此處調用count1 。 在使用前聲明它

int count1(struct node* p);

或將 function 定義移到第一個 function 之前使用它。