《Cracking the Coding Interview》——第9章：递归和动态规划——题目4

2014-03-20 03:08

题目：给定一个集合，返回其幂集。

解法：DFS。

代码：

 1 // 9.4 Return all subsets of a set

 2 #include <cstdio>

 3 #include <vector>

 4 using namespace std;

 5 

 6 void getSubsets(const vector<int> &v, int idx, vector<int> &buffer, vector<vector<int> > &res)

 7 {

 8     if (idx == (int)v.size()) {

 9         res.push_back(buffer);

10     } else {

11         getSubsets(v, idx + 1, buffer, res);

12         buffer.push_back(v[idx]);

13         getSubsets(v, idx + 1, buffer, res);

14         buffer.pop_back();

15     }

16 }

17 

18 int main()

19 {

20     int i, j;

21     vector<vector<int> > res;

22     vector<int> v;

23     vector<int> buffer;

24     int n;

25     

26     while (scanf("%d", &n) == 1 && n > 0) {

27         v.resize(n);

28         for (i = 0; i < n; ++i) {

29             scanf("%d", &v[i]);

30         }

31         

32         getSubsets(v, 0, buffer, res);

33         

34         for (i = 0; i < (int)res.size(); ++i) {

35             printf("[");

36             for (j = 0; j < (int)res[i].size(); ++j) {

37                 if (j == 0) {

38                     printf("%d", res[i][j]);

39                 } else {

40                     printf(" %d", res[i][j]);

41                 }

42             }

43             printf("]\n");

44             res[i].clear();

45         }

46         res.clear();

47         buffer.clear();

48         v.clear();

49     }

50     

51     return 0;

52 }