C++ Input a char instead of int lead to endless loop. How to check the wrong input?

Question

One part of my program: Let user input a series of integer, and then put them into an array.

int n=0;
cout<<"Input the number of data：";
cin>>n;
cout<<"Input the series of data：";
int a[50];
for(i=0; i<n; i++)
{
    cin>>a[i];

}

Then, when user input wrong data such as a character 'a' or 'b'. The program will go into an infinite loop.

How to catch the wrong cin? How to clear the buffer and give user the chance to input a right data again?

Remember that input (and output) streams can be used in boolean expressions, like in an if statement. — Some programmer dude
– Some programmer dude, Commented Mar 5, 2014 at 9:28

const_ref · Accepted Answer · 2018-04-09 14:45:30Z

4

Simply check if the input is a number first and then append it to the array

    int x;
    std::cin >> x;
    while(std::cin.fail())
    {
        std::cin.clear();
        std::cin.ignore(std::numeric_limits<std::streamsize>::max(),'\n');
        std::cout << "Bad entry.  Enter a NUMBER: ";
        std::cin >> x;
    }

    a[i] = x;

edited Apr 9, 2018 at 14:45

answered Mar 5, 2014 at 9:30

const_ref

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1 Comment

const_ref Over a year ago

@YingliYan Accept the answer so others know this solution works :)

Abhishek Bansal · Accepted Answer · 2014-03-05 09:28:53Z

1

Clear the cin state and ignore bad input.

for(i=0; i<n; i++)
{
    while (!(cin>>a[i])) {
        cin.clear();
        cin.ignore(256,'\n');
        cout << "Bad Input, Please re-enter";
    }
}

answered Mar 5, 2014 at 9:28

Abhishek Bansal

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