Define A Range Of Numbers in C/C++

Question

Is there a way that I could divide a range of numbers into certain sub ranges

i.e. If we have the range 1-10

The user inputs 1 3 , 4 7 ,7 10 and we define the range 1-3 as part of one range, 4-7 as another and so on. and if inputed the number 8 for example, we get output as range 3.

Was considering creating an array int arr[10] and as user inputs 1 3 for eg then arr[0]=1 and arr[2]=1 , then for 4 7 as arr[3]=2 and arr[6]=2 . But this misses numbers in between and if we looped from 0 to 2,and 3 to 6. On a larger scale with an array longer than 10 this would be inefficient.

Could someone help me?

Answer 1

Define a range type:

struct range
{
  int low;
  int high;
}

Then define an array of such:

struct range ranges[<some size>] = {0};

Define and implement functions finding the highest high and the lowest lowest low values:

int lowest(struct range * ranges, int * plowest);
int highest(struct range * ranges, int * phighest);

Enter all ranges and stores them in ranges.

Call highest() and lowest() on ranges and you have the outer interval:

struct range range_outer = {0};

/* code reading ranges. */

if (0 != lowest(ranges, &range_outer.lowest))
  fprintf(stderr, "lowest() failed\n");

if (0 != highest(ranges, &range_outer.highest))
  fprintf(stderr, "highest() failed\n");

To help lowest() and highest() it might make sense to sort the ranges, by member low for the former by member high for the latter.

int sort_by_low(struct ranges * ranges); 
int sort_by_high(struct ranges * ranges); 

Sorting arrays can easily be done by using the qsort() function.

Answer 2

A full working implementation:

#include <iostream>
#include <vector>

using namespace std;

typedef struct
{
    int min; int max; int range;
} RANGE;

int InRange(int num, RANGE range)
{
    if (num >= range.min && num <= range.max)
        return 1;
    return 0;
}

int main()
{
    vector<RANGE> list; int count = 0, rangesCount = 0;
    puts("How many ranges?");
    cin >> rangesCount;
    puts("Input the range defenitions as a min-max-range pairs(Enter min, then enter      max, then enter the output range):");
for (int i = 0; i < rangesCount; i++)
{
    RANGE range;
    cin >> range.min;
    cin >> range.max;
    cin >> range.range;
    list.push_back(range);
}

while (1)
{
    puts("Now, enter a value, to know in what range it exist:");
    int num;
    cin >> num;
    for (int i = 0; i < rangesCount; i++)
    {
        RANGE r = list.at(i);
        int included = InRange(num, r);
        if (included)
        {
            cout << "The output range is " << r.range << "\n\n";
        }
    }
}
}

Many things can be improved, and you can tailor it to your needs.