使用malloc的X和y座標的N邊多邊形

Question

我使用Malloc來存儲用戶輸入到程序中的2個座標x和y。用戶需要輸入一個多邊形所具有的N面的數量，並根據N面的數量輸入x和y座標，程序將計算N面多邊形的周長。

編輯：找到了解決方案問題

認識到索引不應少於或等於邊數。

#include <stdio.h> 
#include <stdlib.h> 
#include <math.h> 

double perimeter(int sides, double* polygon_vert_x,double* polygon_vert_y){ 

/* Iteration counter. */ 
    int iloopx; 
    /*variables of type double*/ 
    /*perimeter to store the result of 
    sqaure root*/ 
    /*dx and dy are used to store values 
    of x and y co-ordinates calculation*/ 
    double perimeter, dx, dy; 
    /*initialize perimeter to 0.0*/ 
    perimeter = 0.0; 
    /* calculate perimeter using loops*/ 
    for(iloopx = 0; iloopx < sides; iloopx++) 
    { /*Total length of sides with pythagorean theorem*/ 
     /*distance */ 
     dx = polygon_vert_x[(iloopx+1)%sides] - polygon_vert_x[iloopx]; 
     dy = polygon_vert_y[(iloopx+1)%sides] - polygon_vert_y[iloopx]; 
     /*accumlation*/ 
     perimeter+=sqrt(dx * dx + dy * dy); 
    } 
    /*return total value*/ 
    return perimeter; 

} 

int main(){ 

double perimet; 
int n; 
int count =0; 
double *polygon_vert_x; 
double *polygon_vert_y; 

/*input number of side*/ 
scanf("%d", &n); 

/* Allocate Memory of N-size */ 
polygon_vert_x = malloc(sizeof(double)* n); 
polygon_vert_y = malloc(sizeof(double)* n); 

/*input x-cords, y-cords*/ 
for(count=0; count < n; count++) 
{ 
    /* Get User Input N-Times */ 
    scanf("%lf %lf", &polygon_vert_x[count], &polygon_vert_y[count]); 
} 

/* calculate the perimeter of the polygon */ 
    perimet = perimeter(n, polygon_vert_x, polygon_vert_y); 
    printf("The perimeter length is %.2f units.\n", perimet); 

    return 0; 

} 

Answer 1

這會工作。請注意使用%環繞。這樣你就不必分別處理第一點和最後一點。

#include <stdio.h> 
#include <stdlib.h> 
#include <math.h> 


enum {x, y}; 

double perimeter(int side, double* polygon_vert_x,double* polygon_vert_y); 
double side(double *p1, double *p2); 


int main(){ 

double perimet; 
int n; 
int count =0; 
double *polygon_vert_x; 
double *polygon_vert_y; 

/*input number of side*/ 
scanf("%d", &n); 

/* Allocate Memory of N-size */ 
polygon_vert_x = malloc(sizeof(double)* n); 
polygon_vert_y = malloc(sizeof(double)* n); 

/*input x-cords, y-cords*/ 
for(count=0; count < n; count++) 
{ 
// printf("%d",count); 
    /* Get User Input N-Times */ 
    scanf("%lf %lf", &polygon_vert_x[count], &polygon_vert_y[count]); 
} 

/* calculate the perimeter of the polygon */ 
    perimet = perimeter(n, polygon_vert_x, polygon_vert_y); 
    printf("The perimeter length is %.2f units.\n", perimet); 

    return 0; 

} 

double perimeter(int sides, double* polygon_vert_x,double* polygon_vert_y){ 

    double perimeter; 

    perimeter = 0.0; 
    int i; 
    for(i = 0; i < sides; i++) 
    { 
     double p[2] = {0.0,0.0}; 
     p[x] = polygon_vert_x[i]; 
     p[y] = polygon_vert_y[i]; 
     double p1[2] = {0.0,0.0}; 
     p1[x] = polygon_vert_x[(i+1)%sides]; 
     p1[y] = polygon_vert_y[(i+1)%sides]; 
     perimeter+=side(p,p1); 
    } 
    /*return total value*/ 
    return perimeter; 
} 

/* calculate length of side */ 
double side(double *p1, double *p2) 
{ 
double s1, s2, s3; 

s1 = (p1[x] - p2[x]); 
s2 = (p1[y] - p2[y]); 
s3 = (s1 * s1) + (s2 * s2); 

return sqrt(s3); 
}