Introduction to C language (8)

1. How many days are there in a year or a month

Title Description

Give you a year and month , How many days in the month

Input

A year （ Positive integer ）, A month （1-12）, There is a space between

Output

Days of the month , Take a line alone .

The sample input  

2012 2

Sample output  

29
#include<stdio.h>
main()
{
 int a,b,c;
 scanf(&quot;%d %d&quot;,&a,&b);
 switch(b)
 {
 case 4:
 case 6:
 case 9:
 case 11: c=30;break;
 case 2:
 if(a%4==0&&a%100!=0||a%400==0)
 c=29;
 else
 c=28;
 break;
 default:c= 31; 
 } 
 printf(&quot;%d&quot;,c);
} 

2. arithmetic

Title Description

Give you a simple four arithmetic expressions , Contains two real numbers and an operator , Please program and calculate the result

Input

The format of the expression is ：s1 op s2, s1 and s2 It's two real numbers ,op Represents an operator (+,-,*,/), It can also be other characters . Note that there is a space on each side of the operator .

Output

If the operator is legal , Output the value of the expression ; If operator is illegal or division is performed, divisor is 0, The output "Wrong input!". Keep two digits after the decimal point of the final result .

The sample input  

1.0 + 1.0

Sample output  

2.00

Tips

Divisor is 0, use |s2|＜1e-10( namely 10 Of -10 Power ） Judge

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
int main()
 
{
 double x,y;
 char op;
 scanf(&quot;%lf %c %lf&quot;,&x,&op,&y);
 switch(op){
case'+':printf(&quot;%.2f\n&quot;,x+y);break;
case'-':printf(&quot;%.2f\n&quot;,x-y);break;
case'*':printf(&quot;%.2f\n&quot;,x*y);break;
case'/':if(fabs(y)<1e-10)
 printf(&quot;Wrong input!\n&quot;);
 else printf(&quot;%.2f\n&quot;,x/y);break;
default:printf(&quot;Wrong input!\n&quot;);
 } return 0;
}

3. Absolute maximum

Title Description

Input 3 It's an integer , Output the number with the largest absolute value .

Input

The input contains 3 individual int Range of integers , Space off .

Output

Output the number with the largest absolute value among the three numbers , Take a line alone . If the number with the largest absolute value is not unique , Then output the first one . for example , If the input is 1 -3 3, The output of -3; If the input is 1 3 -3 The output of 3.

The sample input  

1 2 -3

Sample output  

-3
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
int main()
 
{
 int a,b,c,x,y,z,m;
 scanf(&quot;%d %d %d&quot;,&a,&b,&c);
 x=fabs(a);
 y=fabs(b);
 z=fabs(c);
 if (x>=y)
 m=a;
 else if(y>=z)
 m=b;
 else
 m=c;
 printf(&quot;%d&quot;,m);
 
 return 0;
}

4.n Sum the numbers

Title Description

Enter an integer n and n It's an integer , Output this n The sum of integers .

Input

There are two lines of input ： The first line is a positive integer n, The second line is n It's an integer .

Output

Output an integer , namely n The number and . The output is on a single line .

The sample input  

3
7 3 2

Sample output  

12
#include <stdio.h>
#include <stdlib.h>
int main()
 
{
 int i,n,score,sum;
 sum=0;
 scanf(&quot;%d&quot;,&n);
 for(i=1;i<=n;i++){
 scanf(&quot;%d&quot;,&score);
 sum+=score;
 }
printf(&quot;%d&quot;,sum);
 
 return 0;
}

5. Summation of sequences 1

Title Description

Enter an integer n, Output sequence 1+1/3+1/5+…… front n Sum of items .

Input

Enter only one positive integer n.

Output

The result is reserved 2 Decimal place , Take a line alone

The sample input  

3

Sample output  

1.53
#include <stdio.h>
#include <stdlib.h>
 
int main()
{
 int i ,n;
 double sum=0;
 scanf(&quot;%d&quot;,&n);
 for(i=1;i<=n;i++)
 {
 sum=sum+1*1.0/(2*i-1);
 }
 printf(&quot;%.2lf&quot;,sum);
 return 0;
}