Point inside a polygon

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Point inside a polygon

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#1 by (2 votes)
#2 by (0 votes)

1

I need to create a function that checks whether a point is inside a polygon. For that, I researched the internet some solutions that could help me. I found one that seems to be of great help, but in one of the functions needed to run the main function, there was an error. The function is as follows:

// A função checa se o ponto Q está no segmento PR.
bool NoSegmento(Ponto P, Ponto Q, Ponto R)
{
    if (Q.x <= max(P.x, R.x) && Q.x >= min(P.x, R.x) && Q.y <= max(P.y, R.y) 
&& Q.y >= min(P.y, R.y))
        return true;
    return false;
}

However, when compiling, I get some warnings and errors, for example:

implicit declaration of function 'max' [-Wimplicit-function-declaration]|
implicit declaration of function 'min' [-Wimplicit-function-declaration]|
undefined reference to 'max'|
undefined reference to 'min'|

I would like to know if the MAX and MIN functions are functions of some library and what is the purpose of sweating the bool type for the function.

c c++

asked by anonymous 27.06.2017 / 17:28

2 answers

0

The min and max functions are from the C ++ algorithm library see the reference in the documentation

Add in your code:

#import <algorithm>

and modify its function to use the namespace std:

std::min() e std::max()

27.06.2017 / 18:24

Fill a ListView in Xamarin with data Query error by date

score 2 · Accepted Answer

This function checks whether a Ponto is contained within the area occupied by a Rectangle. The points P and R are the coordinates of two opposite vertices of this Rectangle:

Assuming that Ponto looks something like this:

typedef struct _Ponto
{
    int x;
    int y;
} Ponto;

To compile your code in C++ :

#include <algorithm>

bool NoRetangulo( Ponto P, Ponto Q, Ponto R )
{
    return( (Q.x <= std::max(P.x, R.x)) && (Q.x >= std::min(P.x, R.x)) &&
            (Q.y <= std::max(P.y, R.y)) && (Q.y >= std::min(P.y, R.y)) );
}

To compile your code in C :

#define max(a,b)  ( (a > b) ? a : b )
#define min(a,b)  ( (a < b) ? a : b )

int NoRetangulo( Ponto P, Ponto Q, Ponto R )
{
    return( (Q.x <= max(P.x, R.x)) && (Q.x >= min(P.x, R.x)) &&
            (Q.y <= max(P.y, R.y)) && (Q.y >= min(P.y, R.y)) );
}

Improving the idea (in C++ ):

#include <algorithm>


typedef struct Retangulo_
{
    Ponto a;
    Ponto b;
} Retangulo;


int NoRetangulo( Retangulo R, Ponto X )
{
    return( (X.x <= std::max(R.a.x, R.b.x)) && (X.x >= std::min(R.a.x, R.b.x)) &&
            (X.y <= std::max(R.a.y, R.b.y)) && (X.y >= std::min(R.a.y, R.b.y)) );
}