为什么 printf 不使用字符串在 c 中打印任何内容？

如何解决为什么 printf 不使用字符串在 c 中打印任何内容？

> printf("名称: %s\n",temp->name);

这不会在我的输出中打印任何内容，但如果我使用 %C 代替它打印字符串的第一个字符。

这是我的完整代码：

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

struct lkg {
    char *name;
    char *gender;
    struct lkg *link;
} *new,*temp,*front = NULL,*rear = NULL,*new2,*front2 = NULL,*rear2 = NULL,*temp2;

int isempty1() {
    return (front == NULL);
}

void enqueue1(char *data,char *gend) {
    new = malloc(sizeof(struct lkg));
    new->name = data;
    new->gender = gend;
    if (isempty1) {
        front = rear = new;
        printf("\ninsertion sucess\n");
        printf("\n__________________\n");
    } else {
        rear->link = new;
        rear = new;
    }
}

int isempty2() {
    return (front2 == NULL);
}

void enqueue2(char *data,char *gend) {
    new2 = malloc(sizeof(struct lkg));
    new2->name = data;
    new2->gender = gend;
    if (isempty2) {
        front2 = rear2 = new2;
    } else {
        rear2->link = new2;
        rear2 = new2;
    }
}

void displayA() {
    temp = front;
    while (temp != NULL) {
        printf("Name: %s\n",temp->name);
        temp = temp->link;
    }
}

void displayB() {
    temp2 = front2;
    while (temp2 != NULL) {
        printf("Name: %c",temp2->name);
        temp2->link = temp2;
    }
}

void main() {
    int choice;
    char *name,*gender;
        
    do {
        printf("press 1 to enter enroll in LKG A \n Press 2 to enter enroll in LKG B\n press -1 to exit:\n");
        scanf("%d",&choice);
        if (choice == 1) {
            printf("you are enrolling for lkgA\n");
            printf("enter the name and gender:\n");
            scanf("%s%s",&name,&gender);
            enqueue1(name,gender);
        } else
        if (choice == 2) {
            printf("you are enrolling for lkg- B");
            printf("enter the name and gender");
            scanf("%s%s",&gender);
            enqueue2(name,gender);
        } else {
            printf("not a valid choice");
            break;
        }
    } while (choice != -1);
    displayA();
    displayB();       
}

我也尝试过 \n 和 fflush，但在我的场景中不起作用。我想我在指针中犯了错误，但不知道如何解决问题。

解决方法

您的代码中存在多个问题：

• 您将未初始化的指针传递给 scanf() 以进行 %s 转换。您应该改为传递指向实际 char 数组的指针。
• enqueue 函数必须复制参数字符串，因为它们将被下一个输入覆盖。
• main 的返回类型为 int，如果成功，应该返回 0。
• 您应该将大部分全局变量设为本地变量。

这是修改后的版本：

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

struct lkg {
    char *name;
    char *gender;
    struct lkg *link;
} *front = NULL,*rear = NULL,*front2 = NULL,*rear2 = NULL;

int isempty1() {
    return (front == NULL);
}

void enqueue1(char *data,char *gend) {
    struct lkg *new = malloc(sizeof(struct lkg));
    new->name = strdup(data);
    new->gender = strdup(gend);
    if (isempty1) {
        front = rear = new;
        printf("\ninsertion success\n");
        printf("\n__________________\n");
    } else {
        rear->link = new;
        rear = new;
    }
}

int isempty2() {
    return (front2 == NULL);
}

void enqueue2(char *data,char *gend) {
    struct lkg *new = malloc(sizeof(struct lkg));
    new->name = strdup(data);
    new->gender = strdup(gend);
    if (isempty2) {
        front2 = rear2 = new;
    } else {
        rear2->link = new;
        rear2 = new;
    }
}

void displayA() {
    struct lkg *temp = front;
    while (temp != NULL) {
        printf("Name: %s\n",temp->name);
        temp = temp->link;
    }
}

void displayB() {
    struct lkg *temp = front2;
    while (temp != NULL) {
        printf("Name: %c",temp->name);
        temp->link = temp;
    }
}

int main() {
    int choice;
    char name[100],gender[10];
        
    do {
        printf("Enter 1 to enter enroll in LKG A\n"
               "Enter 2 to enter enroll in LKG B\n"
               "Enter -1 to exit:\n");
        if (scanf("%d",&choice) != 1)
            break;
        if (choice == 1) {
            printf("you are enrolling for lkgA\n");
            printf("enter the name and gender:\n");
            scanf("%99s%9s",&name,&gender);
            enqueue1(name,gender);
        } else
        if (choice == 2) {
            printf("you are enrolling for lkgB\n");
            printf("enter the name and gender:\n");
            scanf("%99s%9s",&gender);
            enqueue2(name,gender);
        } else {
            printf("not a valid choice\n");
            break;
        }
    } while (choice != -1);
    displayA();
    displayB();
    return 0;      
}