《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：

// 9.4 Return all subsets of a set
#include <cstdio>
#include <vector>
using namespace std;

void getSubsets(const vector<int> &v, int idx, vector<int> &buffer, vector<vector<int> > &res)
{
    if (idx == (int)v.size()) {
        res.push_back(buffer);
    } else {
        getSubsets(v, idx + 1, buffer, res);
        buffer.push_back(v[idx]);
        getSubsets(v, idx + 1, buffer, res);
        buffer.pop_back();
    }
}

int main()
{
    int i, j;
    vector<vector<int> > res;
    vector<int> v;
    vector<int> buffer;
    int n;
    
    while (scanf("%d", &n) == 1 && n > 0) {
        v.resize(n);
        for (i = 0; i < n; ++i) {
            scanf("%d", &v[i]);
        }
        
        getSubsets(v, 0, buffer, res);
        
        for (i = 0; i < (int)res.size(); ++i) {
            printf("[");
            for (j = 0; j < (int)res[i].size(); ++j) {
                if (j == 0) {
                    printf("%d", res[i][j]);
                } else {
                    printf(" %d", res[i][j]);
                }
            }
            printf("]
");
            res[i].clear();
        }
        res.clear();
        buffer.clear();
        v.clear();
    }
    
    return 0;
}