c++ program to find prime numbers in a given range

Cpp tutorial to find prime numbers between given range

• Write a c++ program in which user will enter start and end of range in integer 
• Program should display every prime number between range and at the end total number of prime numbers found in range.
• Do the same program with separate function which receives two parameters for range calculate result and display output like first code
• Use any C++ compiler codeBlocks Recommended

Cpp Tutorial covers the following concepts

• Nested for loop 
• if statement
• functions in C++
• sqrt() math.h header file
  
  Code
  Compiler Used to code: CodeBlocks c++ Compiler

#include<iostream>
#include<math.h>
using namespace std;
int main()
{
    int startNum,endNum;
    int found=0,count=0;
    cout<<"Enter Number START of Range:  ";
    cin>>startNum;
    cout<<"Enter Number END of Range:  ";
    cin>>endNum;
    for(int i=startNum;i<=endNum;i++)
       {
           for(int j=2;j<=sqrt(i);j++)
               {
               if(i%j==0)
                  count++;
               }
               if(count==0&&i!=1)
               { found++;
                 cout<<"Prime Number -> "<<i<<endl;
                 count=0;
               }
               count=0;
       }

 cout<<"Total Prime Number Between Range "<<startNum<<" to

 "<<endNum<<" = "<<found<<endl;
 return 1;
}

Output : range is 1 to 10

same Code with a function

#include<iostream>
#include<math.h>
using namespace std;
void calculatePrime(int startNum, int endNum);

int main()
{
    int startNum,endNum;
    cout<<"Enter Number START of Range:  ";
    cin>>startNum;
    cout<<"Enter Number END of Range:  ";
    cin>>endNum;

    calculatePrime(startNum,endNum);
 return 1;
}

void calculatePrime(int startNum, int endNum)
{      int found=0,count=0;


    for(int i=startNum;i<=endNum;i++)
       {
           for(int j=2;j<=sqrt(i);j++)
               {
               if(i%j==0)
                  count++;
               }
               if(count==0&&i!=1)
               { found++;
                 cout<<"Prime Number -> "<<i<<endl;
                 count=0;
               }
               count=0;
       }

 cout<<"Total Prime Number Between Range "<<startNum<<" to
        "<<endNum<<" = "<<found<<endl;

}

Another cpp Tutorial here To Find Prime Number 
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Cpp Function to Find Largest and smallest number in array

This Cpp tutorial contains

• Cpp array with random integer values
• Passing array to function
• if statement with in for loop
• Calculate result in function and display

 Compiler used: CodeBlocks Cpp Compiler

Write a program which generates some random number and store in array after it program pass array to a function which calculates maximum and minimum number in array and display it use any Cpp Compiler to code.

How program works

• Declare array of size 10
• Using for loop assign array indexes with random values between 1 and thousand
• Call the function and pass array and its size as argument
• Function declares two integers max and min and assign both integers with arrays first index value
• Then with in for loop there are two if condition first check is for minimum number and second check is for maximum number
• Finally program display the output values of both integers min and max

      Cpp Code

1.  #include <iostream>
2. #include <stdlib.h>
3. using namespace std;
4. void FindMaxMin(int *array, int size)
5. {        int min,max;
6.          min=max=array[0];
7.          for(int i=0;i<size;i++)
8.          {
9.              if(array[i]<min)
10.                min=array[i];
11.             else if(array[i]>max)
12.                max=array[i];
13.          }
14.  cout<<"Minimum Number  = "<<min<<endl;
15.  cout<<"Maximum Number = "<<max<<endl;
16. }
17. int main()
18. {
19.     int array[10];
20.     for(int i=0;i<=9;i++)
21.         {
22.          array[i]=rand()%1000+1;
23.          cout<<"array ["<<i<<"]"<<"= "<<array[i]<<endl;
24.         }
25.     FindMaxMin(array,10);
26. return 0;
27. }

 Sample Output

Another Example without Function more simple
Find Maximum and Minium Number in Array Cpp Code

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Find maximum and minimum number in array c++ code

This Tutorial contains:

• C++ code to find maximum and minimum number in array 
• Program basic working what is used in program and how 
• Dry run of the program with respect to variable values for better under standing

Concept used:

• Arrays in c++ 
• for loop
• if statement
• Random numbers

Write a program to find maximum and minimum number in array using for loop and if statement.
To initialize array use random numbers

Program should display all random elements of array and minimum and maximum number in array
on the output console.

Program Explanation:

• Array size is fixed to 100 to change the size just change the value of size integer
• In the for loop array is initializing with a random number less than 100 to change the range just replace 100 by any desired number and it will produced numbers between 0 to a number you replaced
• In another for loop which programs go through from start of the array to the end and with contains two if statements which checks for both minimum and maximum number in array

c++ code

#include<iostream> #include<cstdlib> #include<ctime> using namespace std; int main() { const int size=50; // array with size of 50 int array[size]; // for random numbers srand(time(0));     for(int i=0;i<size;i++){     // Initializing Array number is less than 100     array[i]=rand()%100;     // Displaying array value     cout<<array[i]<<endl;     }             // initializing max, min                 int max=array[0];                 int min=array[0]; /* scanning array to find    minimum and maximum    number  */ for(int i=0;i<size;i++){     // finding minimum number in array       if(min>array[i]){          min=array[i];       }       //finding maximum number in array       if(max<array[i]){       max=array[i];       } }        // displaying output         cout<<"Maximum Number is :"<<max<<endl;         cout<<"Minimum Number  is:"<<min<<endl; return 0; }

Dry running the code with a simple input so it will be easy to understand the working of program.
let there are five random values in array
55, 3, 2, 44, 100

we will run our main loop in which two if statements are used 
for(int i=0;i<size;i++){
    // finding minimum number in array
      if(min>array[i]){
         min=array[i];
      }
      //finding maximum number in array
      if(max<array[i]){
      max=array[i];
      }
}


before the start of the loop 
max=55; min=55;

i=0;  current array elements 55, 3, 2, 44, 100

min > array[i]
55   > 55    => condition false

max < array[i]
55   > 55    => condition false
------------------------------------------------------

i=1; current array elements 55, 3, 2, 44, 100

min > array[i]
55   > 3    => condition TRUE UPDATE  min =3;

max < array[i]
55    < 3    => condition false  max=55
------------------------------------------------------


i=2; current array elements 55, 3, 2, 44, 100

min > array[i]
3   >    2   => condition TRUE UPDATE  min =2;

max < array[i]
55   <  2    => condition false
------------------------------------------------------


i=3; current array elements 55, 3, 2, 44, 100

min > array[i]2   > 55    => condition false

max < array[i]
55   > 44    => condition false
------------------------------------------------------


i=4; current array elements 55, 3, 2, 44, 100

min > array[i]2   >  100    => condition false

max < array[i]
55   < 100   => condition TRUE UPDATE  max =100;
------------------------------------------------------


Hope this will be helpful.
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Maximum or largest number in array c++ code

Write a C++ program which find largest or maximum number in array using for loop and if statement

Concept used

• Array in c++
• for loop
• if statement

Post contains c++ code and Dry run of code

How program works

• Program first take size of array from user
• Then input element or array one by one
• then show the maximum number in array

c++ code: Using CodeBlocks Compiler

#include<iostream>     using namespace std;     int main()     {     cout<<"Enter The Size Of Array:   ";     int size;     cin>>size;     int array[size], key,i;     // Taking Input In Array     for(int j=0;j<size;j++){     cout<<"Enter "<<j<<" Element : ";     cin>>array[j];     }     //Your Entered Array Is     for(int a=0;a<size;a++){        cout<<"array[ "<<a<<" ]  =  ";        cout<<array[a]<<endl;     }        int  maximum=array[0];        for(int i=0;i<size;i++){           if(array[i]>maximum){               maximum=array[i];           }     }    cout<<"\n\nMaximum Number is in array is :    "<<maximum;    return 0;          }

Sample Output

Sample input output

Dry Run Of Program:
Let size of array is equal to 5
and user enters following numbers
5
6
-7
99
78






Lets dry run main for loop which contains an if statement

which is
     int maximum=array[0];
         for(int i=0;i<size;i++){

          if(array[i]>maximum){
              maximum=array[i];
          }
we have an integer which is maximum = array[0];
so value of maximum= 5;

5, 6, -7, 99, 78

at i=0;
array[i]=5; maximum=5
if(array[i]>maximum)
     5         >    5

condition false


5, 6, -7, 99, 78
at i=1
array[i]=6; maximum=5
if(array[i]>maximum)
     6         >    5

condition True    then maximum=6


5, 6, -7, 99, 78
at i=2
array[i]=-7;  maximum=6
if(array[i]>maximum)
     -7         >    5

condition false



5, 6, -7, 99, 78
at i=3
array[i]= 99;  maximum=6
if(array[i]>maximum)
     99        >   6

condition True  maximum= 99


5, 6, -7, 99, 78
at i=4
array[i]=78;  maximum=99
if(array[i]>maximum)
     78         >    99

condition false



final result is  maximum= 99

so 99 is the maximum number in array


Recommended

There always more than one way to code a program for fast learning change the logic of the program do experiment with code one of the most important is dry run the program on paper it will be very helpful for understand it also improves the logic building

This program will help to understand the working of array, for loop, if statement and assignment operator

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