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Problem description:Please list all of the subsets of a known set including the empty set.
Thinking: the subset's sum of a super set is
(n is the number of the super set element) while a n-bit binary space could express numbers too.So our target is to generate all of the binary numbers in n bit space.Before solving the problem,please look at this point:
11111 01111
+ 1
-------------------
11111 10000
When the number add 1,the current bit will become to 0 and generate a carry if it was 1.Next,the previous bit 1 will become 0 with a carry,too.If its current bit is 0 ,it becomes 1 without a carry and stop the addition.Hence,the program process is clear.
Thinking: the subset's sum of a super set is
11111 01111
+ 1
-------------------
11111 10000
When the number add 1,the current bit will become to 0 and generate a carry if it was 1.Next,the previous bit 1 will become 0 with a carry,too.If its current bit is 0 ,it becomes 1 without a carry and stop the addition.Hence,the program process is clear.
1 #include <stdio.h> 2 #include <math.h> 3 #define MAX 1000 4 5 int n=4;// the number of the set elements 6 int set[MAX]={1,2,3,4}; 7 int path[MAX]={0}; 8 int count=1; 9 10 //prototype 11 void print_set(); 12 13 int main() 14 { 15 int sum=(int)pow(2.0,n)-1; 16 int index,index_re; 17 printf("%d:{}\n",count); 18 for(index=0;index<sum;index++) 19 { 20 for(index_re=n-1;index_re>=0;index_re--) 21 { 22 if(path[index_re]==1) 23 path[index_re]=0; 24 else 25 { 26 path[index_re]=1; 27 break; 28 } 29 } 30 count++; 31 printf("%d:{",count); 32 print_set(); 33 } 34 return 0; 35 } 36 37 void print_set() 38 { 39 int index; 40 for(index=0;index<n;index++) 41 { 42 if(path[index]!=0) 43 printf("%d ",set[index]); 44 } 45 printf("}\n"); 46 }
Reference material: C语言名题精选百则技巧篇 in Chinese.
本文转自NeilHappy 51CTO博客，原文链接：http://blog.51cto.com/neilhappy/1107818，如需转载请自行联系原作者
