任意多边形面积计算（ACM大赛提交题目）

CSharpBoy

1. #include <stdio.h>
   
2. #include <math.h>
   
3. 
   
4. struct point {
   
5.   float x;
   
6.   float y;
   
7. } ptfirst, pt1, pt2, pt0={0, 0};
   
8. 
   
9. float triangsize(struct point pt0, struct point pt1, struct point pt2);
   
10. 
    
11. int main(void)
    
12. {
    
13.   int n;
    
14. 
    
15.   while (scanf("%d", &n) && n>=3) {
    
16.     float sum=0, amount, length;
    
17. 
    
18.     scanf("%f %f", &pt1.x, &pt1.y);
    
19.     scanf("%f %f", &pt2.x, &pt2.y);
    
20.     ptfirst = pt1;          // 保存起始点
    
21.     sum += triangsize(pt0, pt1, pt2);
    
22.     n -= 2;              // 已读取2行
    
23.     for ( ; n>0; n--) {
    
24.       pt1 = pt2;
    
25.       scanf("%f %f", &pt2.x, &pt2.y);
    
26.       sum += triangsize(pt0, pt1, pt2);
    
27.     }
    
28.     sum += triangsize(pt0, pt2, ptfirst);
    
29.     sum = (float)fabs(sum);
    
30.     scanf("%f", &amount);
    
31.     length = amount / sum;
    
32.     printf("BAR LENGTH: %.2f\n", length);
    
33.   }
    
34. 
    
35.   return 0;
    
36. }
    
37. 
    
38. float triangsize(struct point pt0, struct point pt1, struct point pt2)
    
39. {
    
40.   return ((pt0.x*pt1.y + pt1.x*pt2.y + pt2.x*pt0.y) - (pt2.x*pt1.y + pt1.x*pt0.y + pt0.x*pt2.y)) * 0.5f;
    
41. }
    

#include <stdio.h><br /> #include <math.h><br /> <br /> struct point {<br />   float x;<br />   float y;<br /> } ptfirst, pt1, pt2, pt0={0, 0};<br /> <br /> float triangsize(struct point pt0, struct point pt1, struct point pt2); <br /> <br /> int main(void)<br /> {<br />   int n;<br /> <br />   while (scanf("%d", &n) && n>=3) {<br />     float sum=0, amount, length;<br /> <br />     scanf("%f %f", &pt1.x, &pt1.y);<br />     scanf("%f %f", &pt2.x, &pt2.y);<br />     ptfirst = pt1;          // 保存起始点<br />     sum += triangsize(pt0, pt1, pt2);<br />     n -= 2;              // 已读取2行<br />     for ( ; n>0; n--) {<br />       pt1 = pt2;<br />       scanf("%f %f", &pt2.x, &pt2.y);<br />       sum += triangsize(pt0, pt1, pt2);<br />     }<br />     sum += triangsize(pt0, pt2, ptfirst);<br />     sum = (float)fabs(sum);<br />     scanf("%f", &amount);<br />     length = amount / sum;<br />     printf("BAR LENGTH: %.2f\n", length);<br />   }<br /> <br />   return 0;<br /> }<br /> <br /> float triangsize(struct point pt0, struct point pt1, struct point pt2)<br /> {<br />   return ((pt0.x*pt1.y + pt1.x*pt2.y + pt2.x*pt0.y) - (pt2.x*pt1.y + pt1.x*pt0.y + pt0.x*pt2.y)) * 0.5f;<br /> }<br />