Please give me some advice on how to evaluate a maximum region which covers all given regions?

Suppose I have dozens of geographic regions, which can be defined through the use of the following c/c++ structure:

typedef struct tagGEOGRAPHIC_REGION
{    
    float fNorthMost;
    float fSouthMost;
    float fWestMost;
    float fEastMost;
} GEOGRAPHIC_REGION, *PGEOGRAPHIC_REGION;

And I now want to get the maximum region, which will cover all given regions. The function template may look like the following:

const GEOGRAPHIC_REGION& GetMaxRegion(const std:vector<GEOGRAPHIC_REGION>& vRegions)
{  
    ......
}

I can put the four components of GEOGRAPHIC_REGION struct into 4 different float vectors, and then evaluate thei开发者_开发问答r respective maximum values. Finally, the four maxium values can be combined to form the maximum region. I think it must be a simple way to do that. Would you please give me some advice? Thank you very much!

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Can't you just iterate over the vector, and get the maximum north, minimum south, etc, with just one loop?

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I suggest something like this as a starting point:

• see it live: http://ideone.com/LQk8U

• note that I might have your axis direction guessed wrong (you might need to swap some min/max in that case) Edit fixed according to comment "North is positive, and East is positive"

• for a vector, just do std::acummulate(v.begin(), v.end(), v[0]....)

In case your scenarios get more complicated, see the Boost Geometry Library

.

#include <iostream>
#include <numeric>

struct GEOGRAPHIC_REGION
{    
    float fNorthMost;
    float fSouthMost;
    float fWestMost;
    float fEastMost;
};

GEOGRAPHIC_REGION combine(const GEOGRAPHIC_REGION& accum, const GEOGRAPHIC_REGION& tocombine)
{
    GEOGRAPHIC_REGION combined = { 
        std::max(accum.fNorthMost, tocombine.fNorthMost),
        std::min(accum.fSouthMost, tocombine.fSouthMost),
        std::min(accum.fWestMost,  tocombine.fWestMost),
        std::max(accum.fEastMost,  tocombine.fEastMost)
    };
    return combined;
}

int main()
{
    const GEOGRAPHIC_REGION regions[] = 
    {
        { 2,-1,-1,1 },
        { 1,-2,-1,1 },
        { 1,-1,-2,1 },
        { 1,-1,-1,2 },
    };

    GEOGRAPHIC_REGION super = std::accumulate(regions, regions+4, regions[0], combine);

    std::cout << "{ " << super.fNorthMost << ", " 
                      << super.fSouthMost << ", "
                      << super.fWestMost << ", "
                      << super.fEastMost << " }" << std::endl;
}