C language programming case

1. Calculate the average salary of company employees. The number of people in the unit is not fixed, and the salary number is entered from the keyboard. When -1 is entered, the input is completed (the previous input is valid data)

// 平均工资代码
#include <stdio.h>
int main()
{
    
     
  int n=0;
  float wage=0,sum=0,average_wage;
  printf("please input the wage of staff\n(每输入一个工资后空格输入下一个工资，输入-1结束输入):\n");
  while(wage!=-1)
  {
    
    
    scanf("%f",&wage);
    if(wage==-1)
      break;
    sum=sum+wage;
    n++;
  }
  average_wage=sum/n;
  printf("The average wage is %0.2f.\n",average_wage);
  return 0;
} 

2. Enter a year randomly on the keyboard to determine whether it is a leap year.

// 闰年判断代码
#include <stdio.h>
int main()
{
    
    
  int year,leap;
  printf("please input a year:  ");
  scanf("%d",&year);
  if((year%4==0&&year%100!=0||year%400==0))
  {
    
    
    printf("%d是闰年",year);
  }
  else 
  {
    
    
    printf("%d不是闰年\n",year);
  }
  return 0;

3. While loop finds the sum of the first n items

// while循环求前n项和
#include <stdio.h>
int main()
{
    
    
  int i,sum=0;
  i=1;
  while(i<=99)
  {
    
    
    sum=sum+i;
    i++;
  }
  printf("%d\n",sum);
  return 0;
}

4. Find the sum of the first n items in a do while loop

// do while循环求前n项和
#include <stdio.h>
int main()
{
    
    
  int i,sum=0;
  i=1;
  do
  {
    
    
    sum=sum+i;
    i++;
  }
  while(i<=100);
  printf("%d\n",sum);
  return 0;
}

5. The for loop finds the sum of the first n items

// for 循环求n项和
#include <stdio.h>
int main()
{
    
    
  int i,sum=0;
  i=1;
  for(i=1;i<=100;i++)
  {
    
    
    sum=sum+i;
  }
  printf("%d\n",sum);
  return 0;
}

6. Find the sum of the factorials of the first n terms

// 求前n项阶乘之和
#include <stdio.h>
int main()
{
    
    
  int i,sum=0,a=1;
  i=1;
  for(i=1;i<=20;i++)
  {
    
    
    a=i*a;         //阶乘表达式
    sum=sum+a;     //求和
  }
  printf("%d\n",sum);
  return 0;
}

The above codes have been debugged and can be used with confidence.