C++: Intersection Of two ranges

Question

I'm trying to find the intersection of two ranges in C++? For example, if I have one range as [1..14] inclusive, and another as [10..20] inclusive, I want to get [10..14], as that is the intersection between them.

I found a way on SO as follows :

intersection = { std::max(arg1.min, arg2.min), std::min(arg1.max, arg2.max) };
if (intersection.max < intersection.min) {
  intersection.markAsEmpty();
}

I have few variables as follows :

unsigned long long int min1,min2,max1,max2

for which I'm trying to find the the intersection. Then I did the following:

intersection = { std::max(min1, min2), std::min(max1, max2) };
    if (intersection.max < intersection.min) {
      intersection.markAsEmpty();
    }

But this gives the error that unsigned long long int can't be used. How do I use it find the intersection ?

Blind "Copy and Pasting" is not good. In the code you copied, `intersection` is an object of a class type that obviously has members `max` and `min`. — WhiZTiM, Feb 08 '17 at 20:24
This is not a [mcve]. Please fill in the surrounding class definitions required to fully compile this code. — Xirema, Feb 08 '17 at 20:25
Independent of the anyway required [mcve] I would expect that you provide minimum a link when you are talking about someone else code. Just because something is freely available it doesnt mean that you should not mention the original author — 463035818_is_not_an_ai, Feb 08 '17 at 20:30

score 4 · Accepted Answer · edited May 23 '17 at 12:00

I found a way on SO as follows :

intersection = { std::max(arg1.min, arg2.min), std::min(arg1.max, arg2.max) };
if (intersection.max < intersection.min) {
  intersection.markAsEmpty();
}

Blind "Copy and Pasting" is not good. In the code you copied (which you should acknowledge), intersection is an object of a class type that obviously has members max and min.

For your own use case:

unsigned long long int min1,min2,max1,max2 
......
auto Min = std::max(min1, min2);
auto Max = std::min(max1, max2);
if (Min < Max) {
    // There's an intersection. represented by {Min Max}
}

Sam Marinelli · Answer 2 · 2017-02-08T20:39:48.900

0

Try this.

#include <algorithm>
#include <utility>

struct range {
    unsigned long long min, max;
};

range intersect(const range& first, const range& second) {
    return {std::max(first.min, second.min), std::min(first.max, second.max)};
}

You can call it like, e.g., intersect({min1, max1}, {min2, max2}).

edited Feb 08 '17 at 20:39

answered Feb 08 '17 at 20:33

Sam Marinelli

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score 0 · Answer 3 · answered May 23 '20 at 15:08

may be this will help.

say for the range [l1, r1], [l2, r2] intersection between them can be calculated as:

 if ((r1 < l2) ||  (r2 < l1)) then no intersection exits.

 else l = max(l1, l2) and r = min(r1, r2)

just iterate over the range [l, r] to get the intersection values.

C++: Intersection Of two ranges

3 Answers3