问题描述：
算法设计：
算法描述：
#include <iostream> #include <math.h> #include <stdlib.h> #include <string.h> using namespace std; class Circle{ friend float CirclePerm(int ,float *); private: float Center(int t); void Compute(void); void Backtrack(int t); float min,*x,*r; int n; }; float Circle::Center(int t) { float temp = 0; for(int j=1;j<t;j++) { float valuex=x[j]+2.0*sqrt(r[t]*r[j]); if(valuex > temp) temp = valuex; } return temp; } void Circle::Compute(void) { float low = 0, high = 0; for(int i=1;i<=n;i++) { if(x[i]-r[i] < low) low = x[i]-r[i]; if(x[i]+r[i] > high) high = x[i]+r[i]; } if(high-low < min) min = high-low; } void Circle::Backtrack(int t) { if(t>n) Compute(); else for(int j=t;j<=n;j++) { swap(r[t],r[j]); float centerx = Center(t); if(centerx+r[t]+r[1]<min) { x[t] = centerx; Backtrack(t+1); } swap(r[t],r[j]); } } float CirclePerm(int n,float *a) { Circle X; X.n = n; X.r = a; X.min = 100000; float *x = new float [n+1]; X.x = x; X.Backtrack(1); delete [] x; return X.min; } int main() { int n; cout<<"please enter your numbers!:"; cin>>n; float *p = new float [n+1]; cout<<"please enter your circles:"; for(int i=0;i<n;i++) { cin>>p[i]; } cout<<CirclePerm(n,p)<<endl; delete [] p; return 0; }