剑指offer——面试题17：打印从1到最大的n位数

Posted 2021-02-10 acm-jing

用字符串模拟加法：

 1 #include"iostream"
 2 #include"string.h"
 3 using namespace std;
 4 
 5 bool AddOne(char *number,int n);
 6 void PrintNumber(char *number,int n);
 7 
 8 void Print1ToN(int n)
 9 {
10     if(n<=0)
11         return;
12     char *number=new char[n+1];
13     memset(number,‘0‘,n);
14     number[n]=‘‘;
15     while(AddOne(number,n))
16     {
17         PrintNumber(number,n);
18     }
19     delete[] number;
20 }
21 
22 bool AddOne(char *number,int n)
23 {
24     bool isInRange=true;
25     int carry=0;
26     int iDigit;
27     for(int i=n-1;i>=0;i--)
28     {
29         iDigit=number[i]-‘0‘+carry;
30         if(i==n-1)
31             iDigit++;
32         if(iDigit>=10)
33         {
34             if(i==0)
35                 isInRange=false;
36             else
37             {
38                 carry=iDigit/10;
39                 iDigit%=10;
40                 number[i]=iDigit+‘0‘;
41             }
42         }
43         else
44         {
45             number[i]=iDigit+‘0‘;
46             break;
47         }
48     }
49     return isInRange;
50 }
51 
52 void PrintNumber(char *number,int n)
53 {
54     bool firstNoZero=false;
55     for(int i=0;i<n;i++)
56     {
57         if(!firstNoZero&&number[i]!=‘0‘)
58         {
59             firstNoZero=true;
60         }
61         if(firstNoZero)
62             cout<<number[i];
63     }
64     cout<<endl;
65 }
66 int main()
67 {
68     int n;
69     while(cin>>n)
70     {
71         Print1ToN(n);
72     }
73     return 0;
74 }

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 还可以用全排列的思想，递归调用去解决：

 1 #include"iostream"
 2 using namespace std;
 3 
 4 void Print1ToNRecursively(int *number,int length,int index);
 5 void PrintNumber(int *number,int n);
 6 
 7 void Print1ToN(int n)
 8 {
 9     int *number=new int[n];
10 
11     for(int i=0;i<10;i++)
12     {
13         number[0]=i;
14         Print1ToNRecursively(number,n,0);
15     }
16 }
17 
18 void Print1ToNRecursively(int *number,int length,int index)
19 {
20     if(index==length-1)
21     {
22         PrintNumber(number,length);
23         return;
24     }
25     for(int i=0;i<10;i++)
26     {
27         number[index+1]=i;
28         Print1ToNRecursively(number,length,index+1);
29     }
30 }
31 
32 void PrintNumber(int *number,int n)
33 {
34     int i=-1;
35     while(i<n&&number[++i]==0) continue;
36     while(i<n) cout<<number[i++];
37     cout<<endl;
38 }
39 
40 int main()
41 {
42     int n;
43     while(cin>>n)
44     {
45         Print1ToN(n);
46     }
47     return 0;
48 }

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