叉乘如何判断在我的另一篇博客已经讲过。(其实就是懒得再打一遍了
1 #include <map> 2 #include <set> 3 #include <cmath> 4 #include <queue> 5 #include <string> 6 #include <vector> 7 #include <cstdio> 8 #include <cstring> 9 #include <iostream> 10 #include <algorithm> 11 #define forn(i, n) for (int i = 0; i < (n); i++) 12 #define forab(i, a, b) for (int i = (a); i <= (b); i++) 13 #define forba(i, b, a) for (int i = (b); i >= (a); i--) 14 #define mset(a, n) memset(a, n, sizeof(a)) 15 #define fast ios::sync_with_stdio(0), cin.tie(0), cout.tie(0) 16 #define fi first 17 #define se second 18 using namespace std; 19 #define N 5005 20 #define maxn 1005 21 #define inf 0x3f3f3f3f 22 #define ll long long 23 #define ull unsigned long long 24 struct P 25 { 26 int x, y; 27 28 P(){} //构造函数 29 P(int _x,int _y) 30 { 31 x = _x; 32 y = _y; 33 } 34 35 P operator - (const P &b) const 36 { 37 return P(x - b.x, y - b.y); 38 } 39 40 int operator * (const P &b) const //点乘 41 { 42 return x * b.x + y * b.y; 43 } 44 45 int operator ^ (const P &b) const //叉乘 46 { 47 return x * b.y - y * b.x; 48 } 49 50 }; 51 struct L 52 { 53 P p1, p2; 54 55 L(){} 56 L(P _p1,P _p2) 57 { 58 p1 = _p1; 59 p2 = _p2; 60 } 61 62 }a[N]; 63 int cal(P x1,P x2,P x3) 64 { 65 return (x2 - x1) ^ (x3 - x1); 66 } 67 int ans[N], n, m; 68 int x1, x2, Y1, y2; 69 int main() 70 { 71 while(~scanf("%d",&n)) 72 { 73 if(!n) break; 74 scanf("%d %d %d %d %d",&m ,&x1 ,&Y1 ,&x2 ,&y2); 75 forn(i,n) 76 { 77 int f, b; 78 scanf("%d %d",&f ,&b); 79 a[i] = L(P(f,Y1), P(b,y2)); 80 } 81 a[n] = L(P(x2,Y1), P(x2,y2)); 82 mset(ans, 0); 83 forab(i,1,m) 84 { 85 int x, y; 86 scanf("%d %d",&x, &y); 87 P p(x, y); 88 if(cal(p, a[0].p1, a[0].p2) < 0) 89 { 90 ans[0]++; 91 continue; 92 } 93 forab(j,1,n) 94 { 95 if(cal(p, a[j-1].p1, a[j-1].p2) > 0 && cal(p, a[j].p1, a[j].p2) < 0) 96 { 97 ans[j]++; 98 break; 99 } 100 } 101 } 102 forab(i,0,n) 103 { 104 printf("%d: %d ",i ,ans[i]); 105 } 106 printf(" "); 107 } 108 }