Boolean recursive function returning the wrong value

Question

This is a recursive function I did to find out if the given digits in a number are in a decreasing order, I'm sure my base is correct as I see the function does return false for the first few digits, but because the last two are in a decreasing order the function returns true in the end.

I can't figure out how to keep that false value and return it back to the original call for the function.

#include<iostream>
using namespace std;
bool dec(int n);

void main()
{
    cout << dec(1231);
}

bool dec(int n)
{
    bool res;

    if (n < 10)
        return true;
    else
    {
        res = dec(n / 10);
        if ((n / 10) % 10 > n % 10)
            return true;
        else
            return false;
    }
}

if (x) { return true; } else { return false; } is kind of an anti-pattern. Why not just return x;? — cdhowie
– cdhowie, Commented Dec 10, 2014 at 16:42
@kuhaku Not return res, but the whole expression. For example, as per @b4hand's answer: return res && (n / 10) % 10 > n % 10; — cdhowie
– cdhowie, Commented Dec 10, 2014 at 16:45
@cdhowie I didn't know it could be done without the if else. — shinzou
– shinzou, Commented Dec 10, 2014 at 16:50

b4hand · Accepted Answer · 2014-12-10 16:41:42Z

1

You should only return true if res is also true. Try

return (res && (n / 10) % 10 > n % 10);

answered Dec 10, 2014 at 16:41

b4hand

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1 Comment

shinzou Over a year ago

I thought about that but didn't believe it would work because of the recursion, but it does. Thanks.

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