二分高度，算面积的地方有点麻烦，没有用求交点的模板，直接自己按三角形相似手算了一下，写的有点麻烦。
上下界直接取水可放的最高点以及最低点。
自己的长得很挫的代码
1 #include <iostream> 2 #include<cstdio> 3 #include<cstring> 4 #include<algorithm> 5 #include<stdlib.h> 6 #include<vector> 7 #include<cmath> 8 #include<queue> 9 #include<set> 10 using namespace std; 11 #define N 2010 12 #define LL long long 13 #define INF 0xfffffff 14 const double eps = 1e-8; 15 const double pi = acos(-1.0); 16 const double inf = ~0u>>2; 17 struct point 18 { 19 double x ,y; 20 point(double x=0,double y=0):x(x),y(y){} 21 }p[N],q[N],ch[N]; 22 double minz; 23 int n,m; 24 typedef point pointt; 25 pointt operator -(point a,point b) 26 { 27 return point(a.x-b.x,a.y-b.y); 28 } 29 int dcmp(double x) 30 { 31 if(fabs(x)<eps) return 0; 32 return x<0?-1:1; 33 } 34 double dis(point a) 35 { 36 return sqrt(a.x*a.x+a.y*a.y); 37 } 38 double cross(point a,point b) 39 { 40 return a.x*b.y-a.y*b.x; 41 } 42 double getarea(int n,point p[]) 43 { 44 int i; 45 double s = 0; 46 for(i = 2; i < n ; i++) 47 s+=cross(p[i]-p[1],p[i+1]-p[1]); 48 return s/2; 49 } 50 double cal(double r,point p[],int n) 51 { 52 int i,j; 53 int k = 1; 54 for(i = 1; i <= n; i++) 55 if(p[i].y<p[k].y) k = i; 56 57 if(dcmp(r-p[k].y)<=0) return 0.0; 58 59 point p1,p2; 60 int g = 0; 61 for(i = 1; i < k; i++) 62 if(dcmp(p[i].y-r)>=0&&dcmp(p[i+1].y-r)<0) 63 { 64 p1.y = r; 65 double d = r-p[i+1].y; 66 p1.x = d*(p[i].x-p[i+1].x)/(p[i].y-p[i+1].y)+p[i+1].x; 67 break; 68 } 69 70 for(j = k ; j >= i+1; j--) 71 ch[++g] = p[j]; 72 ch[++g] = p1; 73 for(i = k+1 ; i <= n; i++) 74 if(dcmp(p[i-1].y-r)<0&&dcmp(p[i].y-r)>=0) 75 { 76 p2.y = r; 77 double d = r-p[i-1].y; 78 p2.x = d*(p[i].x-p[i-1].x)/(p[i].y-p[i-1].y)+p[i-1].x; 79 break; 80 } 81 ch[++g] = p2; 82 for(j = i-1 ; j > k; j--) 83 ch[++g] = p[j]; 84 85 return fabs(getarea(g,ch)); 86 } 87 int main() 88 { 89 int t,i,a; 90 cin>>t; 91 while(t--) 92 { 93 scanf("%d",&a); 94 scanf("%d",&n); 95 minz = INF; 96 double maxz = INF; 97 for(i = 1; i <= n ;i++) 98 { 99 scanf("%lf%lf",&p[i].x,&p[i].y); 100 maxz = min(maxz,p[i].y); 101 } 102 scanf("%d",&m); 103 for(i = 1; i <= m ;i++) 104 { 105 scanf("%lf%lf",&q[i].x,&q[i].y); 106 maxz = min(maxz,p[i].y); 107 } 108 minz = min(min(p[1].y,p[n].y),min(q[1].y,q[m].y)); 109 double lef = maxz,rig = minz,mid; 110 while(fabs(rig-lef)>eps) 111 { 112 mid = (rig+lef)/2.0; 113 double s1 = cal(mid,p,n),s2 = cal(mid,q,m); 114 if(dcmp(s1+s2-a)>0) 115 rig = mid; 116 else lef = mid; 117 } 118 printf("%.3f ",lef); 119 } 120 return 0; 121 }
感觉不错的别人的代码
1 #include <iostream> 2 #include<cstdio> 3 #include<cstring> 4 #include<algorithm> 5 #include<stdlib.h> 6 #include<vector> 7 #include<cmath> 8 #include<queue> 9 #include<set> 10 using namespace std; 11 #define N 2010 12 #define LL long long 13 #define INF 0xfffffff 14 const double eps = 1e-8; 15 const double pi = acos(-1.0); 16 const double inf = ~0u>>2; 17 struct point 18 { 19 double x ,y; 20 point(double x=0,double y=0):x(x),y(y){} 21 }p[N],q[N],ch[N]; 22 double minz; 23 typedef point pointt; 24 pointt operator -(point a,point b) 25 { 26 return point(a.x-b.x,a.y-b.y); 27 } 28 int dcmp(double x) 29 { 30 if(fabs(x)<eps) return 0; 31 return x<0?-1:1; 32 } 33 double dis(point a) 34 { 35 return sqrt(a.x*a.x+a.y*a.y); 36 } 37 double cross(point a,point b) 38 { 39 return a.x*b.y-a.y*b.x; 40 } 41 42 double getarea(int n,point p[]) 43 { 44 int i; 45 double s = 0; 46 for(i = 1; i < n-1 ; i++) 47 s+=cross(p[i]-p[0],p[i+1]-p[0]); 48 return s/2; 49 } 50 //double cal(double r,point p[],int n) 51 //{ 52 // int i,j; 53 // int k = 1; 54 // for(i = 1; i <= n; i++) 55 // if(p[i].y<p[k].y) k = i; 56 // 57 // r = min(r,minz); 58 // if(dcmp(r-p[k].y)<=0) return 0.0; 59 // 60 // point p1,p2; 61 // int g = 0; 62 // for(i = 1; i < k; i++) 63 // if(dcmp(p[i].y-r)>=0&&dcmp(p[i+1].y-r)<0) 64 // { 65 // p1.y = r; 66 // double d = r-p[i+1].y; 67 // p1.x = d*(p[i].x-p[i+1].x)/(p[i].y-p[i+1].y)+p[i+1].x; 68 // break; 69 // } 70 // // cout<<p1.x<<" "<<p1.y<<endl; 71 // for(j = k ; j >= i+1; j--) 72 // ch[++g] = p[j]; 73 // ch[++g] = p1; 74 // for(i = k+1 ; i <= n; i++) 75 // if(dcmp(p[i-1].y-r)<0&&dcmp(p[i].y-r)>=0) 76 // { 77 // p2.y = r; 78 // double d = r-p[i-1].y; 79 // p2.x = d*(p[i].x-p[i-1].x)/(p[i].y-p[i-1].y)+p[i-1].x; 80 // break; 81 // } 82 // ch[++g] = p2; 83 // for(j = i-1 ; j > k; j--) 84 // ch[++g] = p[j]; 85 // 86 // return fabs(getarea(g,ch)); 87 //} 88 point intersect(point p1,point p2,point p3,point p4){ 89 point p; 90 double a1,b1,a2,b2,c1,c2,d; 91 a1=p1.y-p2.y; b1=p2.x-p1.x; c1=p1.x*p2.y-p2.x*p1.y; 92 a2=p3.y-p4.y; b2=p4.x-p3.x; c2=p3.x*p4.x-p4.x*p3.y; 93 d=a1*b2-a2*b1; 94 p.x=(-c1*b2+c2*b1)/d; 95 p.y=(-a1*c2+a2*c1)/d; 96 return p; 97 } 98 bool pan(point a,point b,double y){ 99 return dcmp(a.y-y)*dcmp(b.y-y)<=0; 100 } 101 double cal(double y,point P[],int n){ 102 103 int i,j,k; 104 int tot=0; 105 point a=point(0,y),b=point(1,y); 106 for(i=1;i<n;i++){ 107 if(pan(P[i],P[i+1],y)){ 108 ch[tot++]=intersect(P[i],P[i+1],a,b); 109 break; 110 } 111 } 112 for(j=i+1;j<n;j++){ 113 ch[tot++]=P[j]; 114 if(pan(P[j],P[j+1],y)){ 115 ch[tot++]=intersect(P[j],P[j+1],a,b); 116 break; 117 } 118 } 119 double area=getarea(tot,ch); 120 return area; 121 } 122 int main() 123 { 124 int t,i,a,n,m; 125 cin>>t; 126 while(t--) 127 { 128 scanf("%d",&a); 129 scanf("%d",&n); 130 minz = INF; 131 for(i = 1; i <= n ;i++) 132 { 133 scanf("%lf%lf",&p[i].x,&p[i].y); 134 minz = min(minz,p[i].y); 135 } 136 scanf("%d",&m); 137 for(i = 1; i <= m ;i++) 138 { 139 scanf("%lf%lf",&q[i].x,&q[i].y); 140 minz = min(minz,q[i].y); 141 } 142 double maxz = min(min(p[1].y,p[n].y),min(q[1].y,q[m].y)); 143 double lef = minz,rig = maxz,mid; 144 while(fabs(rig-lef)>eps) 145 { 146 mid = (rig+lef)/2.0; 147 double s1 = cal(mid,p,n),s2 = cal(mid,q,m); 148 if(dcmp(s1+s2-a)>0) 149 rig = mid; 150 else lef = mid; 151 } 152 printf("%.3f ",lef); 153 } 154 return 0; 155 }