Careercup - Facebook面试题 - 6321181669982208

2014-05-02 09:40

题目链接

原题：

Given a number N, write a program that returns all possible combinations of numbers that add up to N, as lists. (Exclude the N+0=N) 

For example, if N=4 return {{1,1,1,1},{1,1,2},{2,2},{1,3}}

题目：给定一个正整数N，求出所有的由正整数加起来等于N的可能组合(加数保持升序)。比如N = 4的时候，结果是{{1,1,1,1},{1,1,2},{2,2},{1,3}}。

解法：递归解决即可。

代码：

 1 // http://www.careercup.com/question?id=6321181669982208
 2 #include <iostream>
 3 #include <vector>
 4 using namespace std;
 5 
 6 void DFS(int cur, int remain, vector<vector<int> > &result, vector<int> &sum)
 7 {
 8     if (remain == 0) {
 9         result.push_back(sum);
10         return;
11     }
12     if (remain < cur) {
13         return;
14     }
15     
16     int i;
17     for (i = cur; i <= remain; ++i) {
18         if (remain - i != 0 && remain - i < i) {
19             continue;
20         }
21         sum.push_back(i);
22         DFS(i, remain - i, result, sum);
23         sum.pop_back();
24     }
25 }
26 
27 int main()
28 {
29     int n;
30     vector<int> sum;
31     vector<vector<int> > result;
32     int i, j;
33     
34     while (cin >> n && n > 0) {
35         DFS(1, n, result, sum);
36         
37         cout << "{" << endl;
38         for (i = 0; i < (int)result.size(); ++i) {
39             cout << "    {";
40             for (j = 0; j < (int)result[i].size(); ++j) {
41                 j ? cout << ", ", 1: 1;
42                 cout << result[i][j];
43             }
44             cout << "}" << endl;
45         }
46         cout << "}" << endl;
47         
48         sum.clear();
49         for (i = 0; i < (int)result.size(); ++i) {
50             result[i].clear();
51         }
52         result.clear();
53     }
54     
55     return 0;
56 }

 

 posted on 2014-05-02 09:54  zhuli19901106  阅读(171)  评论(0)  编辑  收藏  举报