鱼C论坛 › joker11111 › 日志

joker11111

https://fishc.com.cn/?320612

C语言动态分配内存--malloc函数

热度 1已有 539 次阅读2016-4-20 09:45 |个人分类:C/C++

1.很多人学习C语言的时候常常会犯这样一个错误：

先定义一个N，然后从键盘上输入N的值，接着定义一个大小为N的数组，这样做逻辑完全说得过去，恩，很有道理；

然而呢，在C99标准里这种做法是不被允许的，不过本人亲测，在codeblocks和linux下gcc编译器里是可以运行的，这又是怎么回事？

看了小甲鱼（硬广告）的课才知道这是C11标准新增的内容，这是可以运行的，不过在VC6.0和VS2010就不行了，当时为舍友做一道

学校笔试题（他要申请出国），结果也是困扰我几天（本人比较笨，大家理解下！！！）

先贴题吧：

Question 2
Write a program that:
 Asks the user for number of records, N
 uses one array of Strings of length N to store employee names, an array of double’s of
length N to store the hourly wage, and an array of double’s to store the number of hours
worked.
 reads a list of N employee names, hourly wages, and hours worked, stores them in the
corresponding arrays
 calculates the gross wages for each employee as the product of hourly wages and hours
worked
 calculates the tax for each employee as 10% of the gross wages
 calculates net wages as gross wages minus tax
 keeps track of total gross wages, total taxes, and total net wages
 prints all N employee names, gross wages, tax, net wages in a table
 At the end, prints total gross wages, total taxes, and total net wages

Example session:
INPUT SECTION
Please input the number of records: 5
Record 1 Employee name: John
Record 1 Hourly wage: 10
Record 1 Hours worked: 4.5
Record 2 Employee name: Jill
Record 2 Hourly wage: 11.5
Record 2 Hours worked: 5
Record 3 Employee name: Chris
Record 3 Hourly wage: 11.75
Record 3 Hours worked: 7
Record 4 Employee name: Mitchell
Record 4 Hourly wage: 14
Record 4 Hours worked: 12.5
Record 5 Employee name: Erica
Record 5 Hourly wage: 14.5
Record 5 Hours worked: 15

OUTPUT SECTION
----------------------------------------------------------
Employee name Gross pay Taxes Net pay
----------------------------------------------------------
John $ 45.00 $ 4.50 $ 40.50
Jill $ 57.50 $ 5.75 $ 51.75
Chris $ 82.25 $ 8.23 $ 74.03
Mitchell $ 175.00 $ 17.50 $ 157.50
Erica $ 217.50 $ 21.75 $ 195.75
----------------------------------------------------------
Total $ 577.25 $ 57.73 $ 519.53

解答：

简单来说就是让你从键盘上读取一个数N，然后接着输入N个人的信息（姓名，工作时薪，工作时长），接着按照示例的格式打印出来就可以了

先贴错误示例：

#include <stdio.h>

typedef struct Record

{

char Employee[10];

float H_wage;

float H_worked;

float G_pay;

float Taxes;

float N_pay;

}Record;

int main()

{

int i , N;

float G_pay = 0, Taxes = 0, N_pay = 0;

printf("Please input the number of record:");

scanf("%d", &N);

Record record[N]; //此处引用了键盘读取的N，这在C99中是不可以的

for (i = 0; i < N; i++)

{

printf("Record %d Employee name:", i + 1);

scanf("%s", &record[i].Employee);

printf("Record %d Hourly wage:", i + 1);

scanf("%f", &record[i].H_wage);

printf("Record %d Hours worked:", i + 1);

scanf("%f", &record[i].H_worked);

record[i].G_pay = record[i].H_wage * record[i].H_worked;

record[i].Taxes = record[i].G_pay * 0.1;

record[i].N_pay = record[i].G_pay - record[i].Taxes;

G_pay = G_pay + record[i].G_pay;

Taxes = Taxes + record[i].Taxes;

N_pay = N_pay + record[i].N_pay;

}

printf("\n\nOUTPUT SECTION\n");

printf("---------------------------------------------------------\n");

printf("Employee name Gross pay Taxes Net pay\n");

printf("---------------------------------------------------------\n");

for (i = 0; i < N; i++)

{

printf("%10s $%8.2f $%8.2f $%8.2f\n", record[i].Employee, record[i].G_pay, record[i].Taxes, record[i].N_pay);

}

printf("---------------------------------------------------------\n");

printf(" Total $%8.2f $%8.2f $%8.2f\n", G_pay, Taxes, N_pay);

return 0;

}

正确示例：

#include <stdio.h>

#include <windows.h>

#include <iostream>

typedef struct Record

{

char Employee[10];

float H_wage;

float H_worked;

float G_pay;

float Taxes;

float N_pay;

}Record;

int main()

{

int i , N;

float G_pay = 0, Taxes = 0, N_pay = 0;

printf("Please input the number of record:");

scanf("%d", &N);

Record *record = (Record *)malloc(N * sizeof(Record)); //使用malloc函数进行动态分配内存，C++中用new

for (i = 0; i < N; i++)

{

printf("Record %d Employee name:", i + 1);

scanf("%s", &record[i].Employee);

printf("Record %d Hourly wage:", i + 1);

scanf("%f", &record[i].H_wage);

printf("Record %d Hours worked:", i + 1);

scanf("%f", &record[i].H_worked);

record[i].G_pay = record[i].H_wage * record[i].H_worked;

record[i].Taxes = record[i].G_pay * 0.1;

record[i].N_pay = record[i].G_pay - record[i].Taxes;

G_pay = G_pay + record[i].G_pay;

Taxes = Taxes + record[i].Taxes;

N_pay = N_pay + record[i].N_pay;

}

printf("\n\nOUTPUT SECTION\n");

printf("---------------------------------------------------------\n");

printf("Employee name Gross pay Taxes Net pay\n");

printf("---------------------------------------------------------\n");

for (i = 0; i < N; i++)

{

printf("%10s $%8.2f $%8.2f $%8.2f\n", record[i].Employee, record[i].G_pay, record[i].Taxes, record[i].N_pay);

}

printf("---------------------------------------------------------\n");

printf(" Total $%8.2f $%8.2f $%8.2f\n", G_pay, Taxes, N_pay);

system("pause");

return 0;

}

总之就是酱紫喽，后面的格式打印主要是printf()函数的应用，大家可以参考我日志中的C语言学习摘要中的内容，写的不好，还请笑看哈！

路过

鸡蛋

鲜花

握手

雷人

刚表态过的朋友 (1 人)

天边人影

收藏分享邀请举报

账号		自动登录	找回密码
密码			立即注册

joker11111

C语言动态分配内存--malloc函数

刚表态过的朋友 (1 人)

全部作者的其他最新日志

评论 (0 个评论)