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part 1 format output function printf() and format input function scanf()

ex2_1.cpp   

#include <stdio.h>
int main() {
    int x=1234;
    float f=123.456;
    double m=123.456;
    char ch='a';
    char a[]="Hello, world!"; // Define an array a,String constants are stored continuously in the array hello,world!
    int y=3, z=4; 
    printf("%d %d\n", y, z);
    printf("y=%d, z=%d\n", y,z);
    printf("%8d,%2d\n", x,x);
    printf("%f, %8f, %8.1f, %0.2f, %.2e\n",f,f,f,f,f);
    printf("%lf\n",m);
    printf("%3c\n", ch);
    printf("%s\n%15s\n%10.5s\n%2.5s\n%.3s\n",a,a,a,a,a);
    return 0;
}

ex2_2.cpp

#include <stdio.h>
int main() {
    double x,y;
    char c1,c2,c3;
    int a1,a2,a3;
    scanf("%d%d%d",&a1,&a2,&a3);
    printf("%d,%d,%d\n",a1,a2,a3);
    scanf("%c%c%c",&c1,&c2,&c3);
    printf("%c%c%c\n",c1,c2,c3);
    scanf("%lf,%lf",&x,&y);
    printf("%lf,%lf\n",x,y);
    return 0;
} 

Add address character in parenthesis after scanf&

The defined data type should be the same as that of scanf and printf

part 2 validation content

 #include <stdio.h>
 int main() {
     double a,b,c;
     scanf("%lf %lf %lf", &a, &b, &c);
     
     if(a<0 || b<0 || c<0)
         printf("Can't form a triangle\n");
     else if(a+b>c && a+c>b && b+c>a) {
         if(a==b && a==c)   
             printf("Make an equilateral triangle\n");
         else if(a==b || a==c || b==c)   
             printf("Form isosceles triangle\n");    
         else
             printf("Form a general triangle\n");
     }
     else
         printf("Can't form a triangle\n");
         
     return 0;
} 

 

 

line 14~line 19 are changed to

#include <stdio.h>
 int main() {
     double a,b,c;
     scanf("%lf %lf %lf", &a, &b, &c);
     
     if(a<0 || b<0 || c<0)
         printf("Can't form a triangle\n");
     else if(a+b>c && a+c>b && b+c>a) {
         if(a==b || a==c || a==c){
             if (a==b && a==c)
                 printf("Make an equilateral triangle\n");
             else
                 printf("Form isosceles triangle\n");
         }
     else 
         printf("Form a general triangle\n");
        }
     else
         printf("Can't form a triangle\n");
         
     return 0;
} 

 

Yes.

(2) code before modification

#include <stdio.h>
#include <stdlib.h>
int main() {
    char choice;
   
    printf("Input 0~9 Select the foreground color scheme of the screen background color: \n");
    printf("1-\t Black background green\n");
    printf("2-\t Black with white background\n");
    printf("3-\t Blue bottom white\n");
    printf("Other-\t Black bottom white(default)\n");
    printf("\n Please input, Choose the screen color scheme you want to use:    ");
    
    choice = getchar();
    
    if (choice == '1') {
        system("color 02");
        printf("<This kind of screen color is common in movies and TV series like matrix:)\n"); 
    } 
        
    else if(choice == '2') {
        system("color f0");
        printf("Most editors default to this color:)\n");    
    }
        
    else if(choice == '3') {
        system("color 1f");
        printf("This is not pleasant when the blue screen of the machine breaks down:)\n");
    }
        
    else {
        system("color 0f");
        printf("Console program default small black window:)\n");        
    }
        
        
    printf("programming is fun, just try@_@\n");
    
    
    return 0;
} 

 

The code after modifying int is:

#include <stdio.h>
#include <stdlib.h>
int main() {
    int choice;
    
    printf("Input 0~9 Select the foreground color scheme of the screen background color: \n");
    printf("1-\t Black background green\n");
    printf("2-\t Black with white background\n");
    printf("3-\t Blue bottom white\n");
    printf("Other-\t Black bottom white(default)\n");
    printf("\n Please input, Choose the screen color scheme you want to use:    ");
    
    scanf("%d",&choice);
    
    if (choice == 1) {
        system("color 02");
        printf("<This kind of screen color is common in movies and TV series like matrix:)\n"); 
    } 
        
    else if(choice == 2) {
        system("color f0");
        printf("Most editors default to this color:)\n");    
    }
        
    else if(choice == 3) {
        system("color 1f");
        printf("This is not pleasant when the blue screen of the machine breaks down:)\n");
    }
        
    else {
        system("color 0f");
        printf("Console program default small black window:)\n");        
    }
        
        
    printf("programming is fun, just try@_@\n");
    
    
    return 0;
} 

 

 

part 3 programming exercise

(1) number of palindromes

#include<stdio.h>
int main(){
    int x,a,b,c;
    printf ("Please enter a decimal integer in three digits:\n");
    
    scanf ("%d",&x);
    
    if(x>0&&x<10){
        printf("Calculate its inverse ordinal number...\n");
        printf("%d Positive and negative order are the same\n",x);
    }
    else if(x>=10&&x<100){
        a=x%10;
        b=x/10;
        if(x==a*10+b){
            printf("Calculate its inverse ordinal number...\n");
            printf("%d Positive and negative order are the same\n",x);
        }
        else{
        printf("Calculate its inverse ordinal number...\n");
        printf("%d Positive and negative order are different\n",x);
        }
    } 
    else if(x>=100&&x<1000){
        c=x/100;
        b=(x-c*100)/10;
        a=x%10;
        if(x==a*100+b*10+c){
            printf("Calculate its inverse ordinal number...\n");
            printf("%d Positive and negative order are the same\n",x);    
        }
        else{
            printf("Calculate its inverse ordinal number...\n");
            printf("%d Positive and negative order are different\n",x);
        }        
    }
    else 
        printf("？"); 
    
return 0;    
}

(2) input the year and month from the keyboard to calculate the days of the month.

#include<stdio.h>
int main(){
    printf("Enter year month:\n");
    int year,month,day,leapyear;
    scanf("%d %d",&year,&month);
    leapyear=year%4==0&&year%100!=0||year%400==0;
    if(year<0||month<1||month>12)
        printf("Wrong data entered!");
    else if(month==1||month==3||month==5||month==7||month==8||month==10||month==12)
        day=31;
    else if(month==4||month==6||month==9||month==11)
        day=30;
    else if(month==2)
        day=28+leapyear;
    printf("%d year%d The days of the month are:%d\n",year,month,day);
    return 0;    
} 

 

Input a percentage system score (integer) from the keyboard, and output the grade: excellent, good, medium, pass, fail.

#include<stdio.h>
#include<stdlib.h>
int main(){
    int x;
    scanf("%d",&x);
    printf("Enter score (0~100): %d\n",x);
    switch(x/10){
        case 0 : 
        case 1 : 
        case 2 : 
        case 3 : 
        case 4 : 
        case 5 : printf("Fail,");break;
        case 6 : printf("pass");break;
        case 7 : printf("secondary");break;
        case 8 : printf("good");break;
        case 9 : printf("excellent");break;
        case 10 : printf("excellent");break;
        default:printf("Score is not in valid range");break; 
    }
     return 0;
}

 

 

 

 

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