c - 使用 malloc 具有 X 和 y 坐标的 N 边多边形

Question

我使用 Malloc 来存储用户输入到程序中的 2 个坐标 x 和 y。用户输入多边形的N边数，并根据N边数输入x和y坐标，程序将计算出N边多边形的周长

已编辑:找到此问题的解决方案

意识到索引不应小于或等于边数。

#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

这会起作用。请注意使用 % 进行换行。这样您就不必分别处理第一点和最后一点。

#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);
}