一.題目描述：本書出版之時，美國的個人收入所得稅分為5種不同的稅率，其中最大的稅率大約為40%.以前的情況則更為複雜，稅率也更高。下面所示的程式文字採用25個if語句的合理方法來計算1978年的美國聯邦所得稅。稅率序列為0.14, 0.15, 0.16, 0.17, 0.18.....。序列中此後的計算大於0.01.有何建議呢？

if income <= 2200

tax = 0;

else if income <= 2700

tax = 0.14 * (income - 2200);

else if income <= 3200

tax = 70 + 0.15 * (income - 2700);

else if income <= 3700

tax = 145 + 0.16 * (income -3200);

else if income <= 4200

tax =225 + 0.17 * (income - 3700);

.......

else

tax =53090 + 0.70 * (income - 102200);

採用二分搜尋定位到採用哪個分段函式，然後對應求出結果。

#include <iostream>  
using namespace std;  
  
int basetax[100];  
int lowerbound[100];  
double taxrate[100];  
  
int search(int lowerbound[],int income)  
{  
    int i=0;  
    int j=99;  
    int t=(i+j)/2;  
      
    while(1)  
    {  
          
        if(income - lowerbound[t] < 500 && income - lowerbound[t] >=0)  
            return t;  
        else if(income - lowerbound[t] < 0) //在左側尋找   
            {  
                j=t;  
                t=(i+j)/2;  
                  
            }  
        else  
            {  
                i=t;  
                t=(i+j)/2;  
            }             
    }     
    return  -1;  
      
}  
int main()  
{  
    basetax[0]=0;  
    lowerbound[0]=0;  
    taxrate[0]=0;  
      
    basetax[1]=0;  
    lowerbound[1]=2200;  
    taxrate[1]=0.14;  
      
    for(int i=2;i<100;++i)  
    {  
        basetax[i]=75*i-80;  
        lowerbound[i]=2200 + (i-1)*500;  
        taxrate[i]=(double)(14 + i-1)/100;  
      
    }     
      
        int salary;
<span style="white-space:pre">	</span>cout<<"please input salary:\n";
<span style="white-space:pre">	</span>cin>>salary; 
        int j=search(lowerbound,salary);  
  
        double tax= basetax[j] +   (double)taxrate[j]*(salary -lowerbound[j]);  
      
        cout<<tax<<endl;  
    }  
      
    return 0;  
}