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+=N) 

For example, if N= return {{,,,},{,,},{,},{,}}

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：

 // http://www.careercup.com/question?id=6321181669982208
 #include <iostream>
 #include <vector>
 using namespace std;

 void DFS(int cur, int remain, vector<vector<int> > &result, vector<int> &sum)
 {
     if (remain == ) {
         result.push_back(sum);
         return;
     }
     if (remain < cur) {
         return;
     }

     int i;
     for (i = cur; i <= remain; ++i) {
         if (remain - i !=  && remain - i < i) {
             continue;
         }
         sum.push_back(i);
         DFS(i, remain - i, result, sum);
         sum.pop_back();
     }
 }

 int main()
 {
     int n;
     vector<int> sum;
     vector<vector<int> > result;
     int i, j;

     while (cin >> n && n > ) {
         DFS(, n, result, sum);

         cout << "{" << endl;
         for (i = ; i < (int)result.size(); ++i) {
             cout << "    {";
             for (j = ; j < (int)result[i].size(); ++j) {
                 j ? cout << ", ", : ;
                 cout << result[i][j];
             }
             cout << "}" << endl;
         }
         cout << "}" << endl;

         sum.clear();
         for (i = ; i < (int)result.size(); ++i) {
             result[i].clear();
         }
         result.clear();
     }

     return ;
 }