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Second assignment

2020-11-08 10:05:00 【He is a famous Chinese character】

0. Exhibition PTA Total score

1. Summary of this chapter

1.1 Summary of this chapter and 1.2 Summary of programming skills

Variable name ： Little hump nomenclature example ：aB
Function name ： The name of the great hump example ：Ab
c The identifier in a language consists of letters Numbers Underline composition , The first character must be Letters or underscores .
int（ integer ） char( Character ） float( Single precision floating point ） double( Double precision floating point ）typedef( Custom type ）
/ written words / Comment lines
//： Note a single line
（1） Two integers are divided , The result of the operation is an integer .
example ：10/4=2 1/3=0
（2） The remainder
example ：5%6=5 9%4=1 100%4=0（ It means that it can be divisible ）
（3） To convert to floating point , You need to convert one of the numbers into floating-point numbers
example ：10.0/4 10.0/4.0
（1） Format input function scanf()
int Type data %d float Type data %f doouble Type data %lf
example ：scanf("%lf",&x); （ Pay attention to the type of data entered , Control the character with the corresponding format ,& Don't miss it. ）
（2） Format output function printf()
int Type data %d fioat and double Type data are available %f,double The model can also be used %lf
%nf Indicates that the output data is reserved after the decimal point n position
%f The decimal point is reserved by default 6 position
example ：printf("%d %f %.3f",a,b,c);

Generate random number
example ：

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
int main()
{
 int number;             // A variable that defines a random number 
 srand(time(0));         // Produce seeds 
 number = rand() % 100;  // The range of generating random numbers is 0-100
 printf("%d", number);   // Output random number 
 return 0;
}

If the range of random numbers generated is 10-100, The code for the scope is changed to ：number=10+rand()%90;

Relational operator
== equal ！= Unequal
Mathematical functions
Call I / O function , To add #include <stdio.h> Call mathematical function , To add #include <math.h>
Square root function ： sqrt(x) example ： sqrt(4.0)=2.0
Absolute value function ： fabs(x) example ： fabs(-5.0)=5.0
power function ： pow(x,n) example ： pow(4,2)=16
Exponential function exp(x) example ： exp(2.3) The value of is e Of 2.3 Power
Control the number of outputs
%md If the number of digits is less than m, Will automatically fill in the space from the left
%-md If the number of digits is less than m, Will automatically fill in the space from the right
%m.nf m Including the sign place and the decimal point ,n Express reservation n Decimal place
example ：
```
#include <stdio.h>
int main()
{
   int number1,number2;
   double number3;
   scanf("%d %d %lf", &number1,&number2,&number3);
   printf("%5d%-5d%5.3f", number1,number2,number3);
   return 0;
}
```
When the input 30 50 5.5 when , The output is ： Three spaces +3050 Three spaces +5.500

Make the tail without spaces
example ：

#include <stdio.h>
int main()
{
int n = 3;
int i;
int flag = 1;
int number;
int a;
for (i = 1; i <= 3; i++)
{
	scanf_s("%d", &a);
        number = a;
        if (flag == 1)                    // Find the first number , And change the output mode of the following numbers 
{
	flag = 0;
	printf("%d", number);
}
        else
{
	printf("a%d", number);
}
}
    return 0;
}

When the input 30 and 40 and 50 when , The output is 30a40a50, Can realize tail without space

Character data
The data of character type variable is used char To define , And add ''
Commonly used decimal character type constant ASCII code ：'a':97,'A':65,'0':48
Character input and output functions ：
（1）getchar(): Only one character can be read in ,（） There are no parameters in it
（2）putchar(): Output a character , Format ：putchar( Output parameters ）
example ：
```
#include <stdio.h>
int main()
{
char ch;
ch = 97;
printf("%c %d", ch, ch);
    return 0;
}
```
The output is ：ch 97
Logical operations
！： Not ,&&： And ,||： or
&& and || Has a lower priority than the relational operator
Flexible use switch Statement break
example ： Show part of the code
```
case n: case m: case f: ......case z:
 expression ;
break;
```
above case Common expressions
Pseudo code descriptors
example ：
(1）while Conditions
expression
end while
(2) if Conditions
expression
end if

n-- And --n A kind of distinction
example ：

#include <stdio.h>
int main()
{
    int n;
    n = 8;
    printf("%d ", n--);
}

The output is 8

#include <stdio.h>
int main()
{
    int n;
    n = 8;
    printf("%d ", --n);
}

The output is 7

Take a number from a certain bit
example ：
number It means a number ,n A number in one of its bits
bits ：n=number%10
ten ：n=number/10%10
Hundred bit ：n=number/100%10
And so on

Input 3 The number of outputs is maximum or minimum or middle or arranged in order of size
Example ：

The code you started with ：

#include <stdio.h>

int main()
{
    int a,b,c;
    scanf("%d %d %d",&a,&b,&c);
    if(a>b)
    {
        if(b>c)
        {
            printf("x=%d,y=%d,z=%d",c,b,a);
        }
        else if(c>a)
        {
            printf("x=%d,y=%d,z=%d",b,a,c);
        }else
        {
            printf("x=%d,y=%d,z=%d",b,c,a);
        }
    }else
    {
        if(c>b)
        {
            printf("x=%d,y=%d,z=%d",a,b,c);
        }
        else if(a>c)
        {
            printf("x=%d,y=%d,z=%d",c,a,b);
        }else
        {
            printf("x=%d,y=%d,z=%d",a,c,b);
        }
    }
    return 0;
}

What happened ： A lot of code , And the idea is complicated , It's not good for getting things done quickly .
Learn to refer to the code replaced by intermediate quantity ：

#include <stdio.h>
int main()
{
    int number1,number2,number3, temp;
    scanf("%d %d %d", &number1, &number2, &number3);
    if (number1 > number2)
    {
	    temp = number1; 
	    number1 = number2;
	    number2 = temp;
    }
    if (number1 > number3)
    {
	    temp = number1;
	    number1 = number3;
	    number3 = temp;
    }
    if (number2 > number3)
    {
	    temp = number2;
	    number2 = number3;
	    number3 = temp;
    }
    printf("x=%d,y=%d,z=%d", number1, number2, number3);
    return 0;
}

Easy to operate , And the idea is clear .

Calculation 1-1/3+1/5-... A kind of question type （ introduce flag)
Example ：

#include <stdio.h>

int main()
{
    int i;
    int n;
    int flag;
    double sum;
    scanf("%d", &n);
    flag = 1;
    sum = 0;
    for (i = 1; i <= n; i++)
    {
	    sum = sum + flag*i * 1.0 / (2 * i - 1);
	    flag = -flag;
    }
    printf("%.3f", sum);
    return 0;
}

Count the number of digits of an integer
example ：

#include <stdio.h>

int main()
{
    int count, number;
    count = 0;
    scanf_s("%d",&number);
    while (number != 0)
    {
	    count++;
	    number = number / 10;
    }
    printf("%d", count);
    return 0;
}

1.3 Learning experience of this chapter

Through these two weeks of study and review c Language related content , Because during the summer vacation, I have a little understanding of the previous content , So I can keep up with the class content , There is no problem with the structure and content of those statements , But some of the sentences are not very well understood , The basic reason is that there is no clear understanding of the basic content of the sentence , I don't know enough about the details , Including the preview of the textbook is not complete . After that, the class progress is a little fast ⊙ω⊙, Just after the preview, we should preview the next section immediately , A little too late to consolidate their own foundation , In the last two weeks, we have written the branch structure of the topic, and have written the experimental problem set published in class , And preview some topics in the courseware .

2.PTA Experiment assignment

2.1 The day before yesterday

2.1.1 Data processing

Variable ：

year（ year ）( integer ）： The day before yesterday, it might be another year
month（ month ）（ integer ）： The day before yesterday may involve a month change
day( Days ）（ integer ）： It must involve the change of days
Febary( The number of days in February ）： There are different February days between leap year and non leap year
mark（ month /1）（ integer ）： Need to use switch sentence

2.1.2 Code screenshot

A little longer , Separate cut graphs

2.1.3 PTA Submit list and description

Q1: Looking for a long time exactly where programming errors or missing some letters and symbols
A1: The results are moving , Turned out to be case There's no number after it , Add the expression directly .....

Height difference of the best couple

2.2.1 Data processing

Variable ：

sex（ Gender ）( Character ）： Determine gender
n( The number of ）( plastic ）： Judge how many people
i( plastic ): Loop statements use
height( height ）( integer ）： Subject requirements
number( Suitable for height ）( integer ）： The optimum height after conversion

2.2.2 Code screenshot

2.2.3 PTA Submit list and description

The teacher has explained the input related question in class and typed the code , When I write by myself, I first write in vs Debug and correct, so the commit is correct

Step by step debugging ( Tortoise and the hare )

2.3.1 One step debug screenshot

2.3.2 Code screenshot

2.3.3 PTA Submit list and description

Q1： Only partially correct when submitted , Several parts of the judgment are missing
A1: Forget to judge whether the rabbit runs faster than the tortoise , Split the time directly every ten minutes , This leads to a partial lack of judgment .