Problem Solving



  2. Question:Determining if a number is prime in c 
    Answer
    1. #include<stdio.h>
    2.  
    3. int main(){
    4.  
    5.     int num,i,count=0;
    6.     printf("Enter a number: ");
    7.     scanf("%d",&num);
    8.     for(i=2;i<=num/2;i++){
    9.         if(num%i==0){
    10.          count++;
    11.             break;
    12.         }
    13.     }
    14.    if(count==0 && num!= 1)
    15.         printf("%d is a prime number",num);
    16.    else
    17.       printf("%d is not a prime number",num);
    18.    return 0;
    19. }
    Sample output:
Enter a number: 5
5 is a prime number






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  3. Question:How to find prime numbers from 1 to 100 in c 
    Answer
    1. #include<stdio.h>
    2.  
    3. int main(){
    4.     int num,i,count;
    5.   
    6.     for(num = 1;num<=100;num++){
    7.          count = 0;
    8.  
    9.          for(i=2;i<=num/2;i++){
    10.              if(num%i==0){
    11.                  count++;
    12.                  break;
    13.              }
    14.         }
    15.         
    16.          if(count==0 && num!= 1)
    17.              printf("%d ",num);
    18.     }
    19.   
    20.    return 0;
    21. }
    Output:
2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97






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  4. Question:Write a c program to generate n prime numbers 
    Answer
    1. #include<stdio.h>
    2.  
    3. int main(){
    4.  
    5.     int num,i,count,n;
    6.     printf("Enter max range: ");
    7.     scanf("%d",&n);
    8.  
    9.     for(num = 1;num<=n;num++){
    10.  
    11.          count = 0;
    12.  
    13.          for(i=2;i<=num/2;i++){
    14.              if(num%i==0){
    15.                  count++;
    16.                  break;
    17.              }
    18.         }
    19.         
    20.          if(count==0 && num!= 1)
    21.              printf("%d ",num);
    22.     }
    23.   
    24.    return 0;
    25. }
    Sample output:
Enter max range: 50
2 3 5 7 11 13 17 19 23 29 31 37 41 43 47






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  5. Question:C code to display prime numbers within a range 
    Answer
    1. #include<stdio.h>
    2.  
    3. int main(){
    4.  
    5.     int num,i,count,min,max;
    6.  
    7.      printf("Enter min range: ");
    8.      scanf("%d",&min);
    9.  
    10.     printf("Enter max range: ");
    11.     scanf("%d",&max);
    12.  
    13.     for(num = min;num<=max;num++){
    14.  
    15.          count = 0;
    16.  
    17.          for(i=2;i<=num/2;i++){
    18.              if(num%i==0){
    19.                  count++;
    20.                  break;
    21.              }
    22.         }
    23.         
    24.          if(count==0 && num!= 1)
    25.              printf("%d ",num);
    26.     }
    27.   
    28.    return 0;
    29. }
    Alternate with while loop
    1. #include<stdio.h>
    2.  
    3. int main(){
    4.  
    5.    int num,i,count,min,max;
    6.  
    7. printf("Enter min range: ");
    8.     scanf("%d",&min);
    9.  
    10.     printf("Enter max range: ");
    11.     scanf("%d",&max);
    12.  
    13.     num = min;
    14.     while(num<=max){
    15.  
    16.          count = 0;
    17.          i=2;
    18.  
    19.          while(i<=num/2){
    20.              if(num%i==0){
    21.                  count++;
    22.                  break;
    23.              }
    24.              i++;
    25.         }
    26.         
    27.          if(count==0 && num!= 1)
    28.              printf("%d ",num);
    29.  
    30.          num++;
    31.     }
    32.   
    33.    return 0;
    34. }
    Sample output:
Enter min range: 10
Enter max range: 50
11 13 17 19 23 29 31 37 41 43 47






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  6. Question:C program to find sum of prime numbers within a range. 
    Answer
    1. #include<stdio.h>
    2.  
    3. int main(){
    4.  
    5.     int num,i,count,min,max,sum=0;
    6.  
    7.      printf("Enter min range: ");
    8.      scanf("%d",&min);
    9.  
    10.     printf("Enter max range: ");
    11.     scanf("%d",&max);
    12.  
    13.     for(num = min;num<=max;num++){
    14.  
    15.          count = 0;
    16.  
    17.          for(i=2;i<=num/2;i++){
    18.              if(num%i==0){
    19.                  count++;
    20.                  break;
    21.              }
    22.         }
    23.         
    24.          if(count==0 && num!= 1)
    25.              sum = sum + num;
    26.     }
    27.  
    28.     printf("Sum of prime numbers is: %d ",sum);
    29.   
    30.    return 0;
    31. }
    Sample output:
Enter min range: 50
Enter max range: 100
Sum of prime numbers is: 732






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