Sorting numbers digit wise

Question

I have N numbers and I want to sort each number by digit. ( In my original problem I want to make the largest number by these (greedy approach)) For ex - If we have 5 numbers 9 1000 845 8000 56 In first step I will pick 9 as 9 is the highest of all 1st digit of numbers

In second step ( as 9 is already picked), next highest first digit is 8, but when 2 or more numbers have same digit I will compare their next digit so I will pick 845.

In this if I sort I will get the following result 9 845 8000 56 1000.

My question is how can implement this in c++ ?

Thanks in advance

Is it correct that in your sorting, 0 is after 4? Because that calls for a complete custom compare, as in numeric as well as lexicographic order, 0 < 4... — king_nak
– king_nak, Commented Jul 20, 2020 at 11:30

Ahmed El-sisy · Accepted Answer · 2020-12-31 15:37:04Z

0

You can get the expected result by passing a custom compare function to the sort function.

The compare function may be like this:

bool compare(int a, int b) {
    ostringstream x, y;
    x << a; y << b;
    return x.str() > y.str();
}


...
    sort(array, array+n, compare);
...

In this compare function, we are converting the integer data to string data and simply comparing the string values to get the expected sorted array.

edited Dec 31, 2020 at 15:37

Ahmed El-sisy

33 bronze badges

answered Jul 20, 2020 at 11:26

Masudur Rahman

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1 Comment

0x5453 Over a year ago

One liner:

std::sort(std::begin(array), std::end(array), [](int lhs, int rhs){ return std::to_string(lhs) > std::to_string(rhs); });

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