While loops expression

Question

I'm trying to write a program that asks the user to enter digits between 0 and 1000000 and it outputs the occurrence of a certain number (that the user entered as well)

I've wrote this program and I believe it works well, but I have one issue which is if the while expression is not true, I want to cout a certain message but I don't know where to place it.

Here's my program:

#include <iostream> 
using namespace std;
int main()
{ 
 int n,j=0,key; 
 cout << "Pleaser enter digits\n";
 cin >> n;
 cout << "please enter key number\n";
 cin >> key;

 while (n>0 && n<1000000)
 {
   if(n%10==key)j++; 
      n= n/10;
 }

 cout << "The number " << key << " was found " << j << " time(s)" << endl;
 return 0;  
}

Thanks in advance!

You could just wrap the while loop in an `if` `else` condition block, so `if (n <=0 || n >= 1000000) cout << "invalid params"; else { while...}` — EdChum, Oct 06 '14 at 11:18
You **do** cout a certain message if the while condition is not true. Do you meant "if the while expression is not true *the first time*"? — TobiMcNamobi, Oct 06 '14 at 11:18
@TobiMcNamobi Yes, he meant when user enters value of n not in range (0, 1000000) — Ashwani, Oct 06 '14 at 11:26

score 2 · Accepted Answer · answered Oct 06 '14 at 11:24

2

Use

if(n>0 && n<1000000)
{
    while(n)
    {
       if(n%10==key)
       j++; 
       n= n/10;
    } 
}
else 
cout<<"n is supposed to be between 0 and 1000000";

answered Oct 06 '14 at 11:24

Spikatrix

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user966379 · Answer 2 · 2014-10-06T11:38:13.247

0

Write a if statement before while loop.

     if(!(n>0 && n<1000000))
        {
           cout << "....";
           return -1;
        }

      while(..)

edited Oct 06 '14 at 11:38

answered Oct 06 '14 at 11:25

user966379

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otorrillas · Answer 3 · 2014-10-06T11:34:35.153

As there are no breaks (or no other piece of code that can jump) inside the bucle, everything after the while structure is executed because the expression returned false.

while (n>0 && n<1000000)
{
   if(n%10==key)j++; 
   n= n/10;
}
cout << "While expression not anymore true" << endl;
cout << "The number " << key << " was found " << j << " time(s)" << endl;
return 0;  
}

UPDATE

Based on the comments, it seems that you want to check if the number entered is valid or not. Simply, just check it before the while:

if(not (n>0 and n<1000000)) cout << "Number must be between 0 and 1000000" << endl;
else {
    while (n)
    {
        if(n%10==key)j++; 
        n= n/10;
    }
}
cout << "The number " << key << " was found " << j << " time(s)" << endl;
return 0;  
}

While loops expression

3 Answers3