输入数字n,按顺序从打印出从1到最大的n位十进制数.比如输入3,也就是最大的3位数是999,那么就打印1.2.3.---999;
方法1:非递归
1 #include "stdafx.h" 2 #include <iostream> 3 #include <exception> 4 using namespace std; 5 void PrintNumber(char* number) 6 { 7 bool isBeginning0 = true; 8 int nLength = strlen(number); 9 for(int i = 0;i<nLength;++i) 10 { 11 if(isBeginning0&&number[i]!=‘0‘) 12 isBeginning0 = false; 13 if(!isBeginning0) 14 { 15 printf("%c",number[i]); 16 } 17 18 } 19 printf("\t"); 20 } 21 bool Increment(char* number) 22 { 23 bool isOverflow = false; 24 int nTakeOver = 0; 25 int nLength = strlen(number); 26 for(int i = nLength-1;i>=0;i--){ 27 int nSum = number[i]-‘0‘+nTakeOver; 28 if(i==nLength-1) 29 nSum++; 30 if(nSum>=10) 31 { 32 if(i==0) 33 isOverflow=true; 34 else 35 { 36 nSum -= 10; 37 nTakeOver=1; 38 number[i]=‘0‘+nSum; 39 40 } 41 } 42 else{ 43 number[i]=‘0‘+nSum; 44 break; 45 } 46 } 47 return isOverflow; 48 49 } 50 void PrintToMaxOfNDigits(int n) 51 { 52 if(n<=0) 53 return; 54 char *number = new char[n+1]; 55 memset(number,‘0‘,n); 56 number[n]=‘\0‘; 57 while(!Increment(number)) 58 { 59 PrintNumber(number); 60 } 61 delete []number; 62 } 63 int _tmain(int argc, _TCHAR* argv[]) 64 { 65 int n = 4; 66 PrintToMaxOfNDigits(n); 67 return 0; 68 }
方法2.递归法，全排列用递归表达，数字的每一位都可能是0-9中的一个数，然后设置下一位。递归结束的条件是我们已经设置了数字的最后一位.
1 #include "stdafx.h" 2 #include <iostream> 3 #include <exception> 4 using namespace std; 5 void PrintNumber(char* number) 6 { 7 bool isBeginning0 = true; 8 int nLength = strlen(number); 9 for(int i = 0;i<nLength;++i) 10 { 11 if(isBeginning0&&number[i]!=‘0‘) 12 isBeginning0 = false; 13 if(!isBeginning0) 14 { 15 printf("%c",number[i]); 16 } 17 18 } 19 printf("\t"); 20 } 21 void Print1ToMaxOfNDigitsRecursively(char* number,int length,int index) 22 { 23 if(index==length-1) 24 { 25 PrintNumber(number); 26 return; 27 } 28 for(int i = 0;i<10;++i) 29 { 30 number[index+1]=i+‘0‘; 31 Print1ToMaxOfNDigitsRecursively(number,length,index+1); 32 } 33 } 34 void Print1ToMaxOfNDigits(int n) 35 { 36 if(n<=0) 37 return; 38 char* number = new char[n+1]; 39 number[n]=‘\0‘; 40 for(int i = 0;i<10;++i) 41 { 42 number[0]=i+‘0‘; 43 Print1ToMaxOfNDigitsRecursively(number,n,0); 44 } 45 delete[] number; 46 47 } 48 int _tmain(int argc, _TCHAR* argv[]) 49 { 50 int n = 4; 51 Print1ToMaxOfNDigits(n); 52 return 0; 53 }