POJ 3187 Backward Digit Sums（dfs） - c++编程基础

Backward Digit Sums

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 4281		Accepted: 2470

Description

FJ and his cows enjoy playing a mental game. They write down the numbers from 1 to N (1 <= N <= 10) in a certain order and then sum adjacent numbers to produce a new list with one fewer number. They repeat this until only a single number is left. For example, one instance of the game (when N=4) might go like this:

    3   1   2   4

      4   3   6

        7   9

         16

Behind FJ's back, the cows have started playing a more difficult game, in which they try to determine the starting sequence from only the final total and the number N. Unfortunately, the game is a bit above FJ's mental arithmetic capabilities.

Write a program to help FJ play the game and keep up with the cows.

Input

Line 1: Two space-separated integers: N and the final sum.

Output

Line 1: An ordering of the integers 1..N that leads to the given sum. If there are multiple solutions, choose the one that is lexicographically least, i.e., that puts smaller numbers first.

Sample Input

4 16

Sample Output

3 1 2 4

Hint

Explanation of the sample:

There are other possible sequences, such as 3 2 1 4, but 3 1 2 4 is the lexicographically smallest.

Source

USACO 2006 February Gold & Silver

这个题意就是给你一个n和m，然后n个数排列后像上面的那样计算出一个数，如果和m想同就ok，输出最小的序列

思路：

直接dfs枚举每个序列，如果有满足结束，不过我代码中有个传地址的地方让我bug了几分钟，细节在代码中

#include
  
   
#include
   
     #include
    
      #include
     
       using namespace std; #define N 20 int a[N],ans[N]; int vis[N]; int n,m; int yes; int fdd(int a[],int n) { if(n==1) return a[0]; int i; for(i=0;i