Vijos 1092 全排列

题目链接

来个水题。。难得的1Y。

 1 #include <cstdio>

 2 #include <cstring>

 3 #include <iostream>

 4 using namespace std;

 5 #define LL __int64

 6 int flag[31],que[31];

 7 LL fact[31];

 8 int n;

 9 LL m;

10 void dfs(LL x,int step)

11 {

12     LL temp = 0;

13     int i;

14     for(i = 1;i <= n;i ++)

15     {

16         if(!flag[i])

17         {

18             if(temp + fact[n-step] >= x)

19             {

20                 flag[i] = 1;

21                 que[step] = i;

22                 dfs(x-temp,step+1);

23                 return ;

24             }

25             temp += fact[n-step];

26         }

27     }

28 }

29 int main()

30 {

31     int i;

32     fact[0] = 1;

33     for(i = 1;i <= 20;i ++)

34     fact[i] = fact[i-1]*i;

35     scanf("%d%I64d",&n,&m);

36     dfs(m,1);

37     for(i = 1;i <= n;i ++)

38     {

39         if(i == 1)

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

41         else

42         printf(" %d",que[i]);

43     }

44     printf("\n");

45     return 0;

46 }