HDU 1027 取數列問題

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Ignatius and the Princess IITime Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 4803    Accepted Submission(s): 2885


Problem DescriptionNow our hero finds the door to the BEelzebub feng5166. He opens the door and finds feng5166 is about to kill our pretty Princess. But now the BEelzebub has to beat our hero first. feng5166 says, "I have three question for you, if you can work them out, I will release the Princess, or you will be my dinner, too." Ignatius says confidently, "OK, at last, I will save the Princess."

"Now I will show you the first problem." feng5166 says, "Given a sequence of number 1 to N, we define that 1,2,3...N-1,N is the smallest sequence among all the sequence which can be composed with number 1 to N(each number can be and should be use only once in this problem). So it‘s easy to see the second smallest sequence is 1,2,3...N,N-1. Now I will give you two numbers, N and M. You should tell me the Mth smallest sequence which is composed with number 1 to N. It‘s easy, isn‘t is? Hahahahaha......"
Can you help Ignatius to solve this problem?
 
InputThe input contains several test cases. Each test case consists of two numbers, N and M(1<=N<=1000, 1<=M<=10000). You may assume that there is always a sequence satisfied the BEelzebub‘s demand. The input is terminated by the end of file.
 
OutputFor each test case, you only have to output the sequence satisfied the BEelzebub‘s demand. When output a sequence, you should print a space between two numbers, but do not output any spaces after the last number.
 
Sample Input

6 411 8

 
Sample Output

1 2 3 5 6 41 2 3 4 5 6 7 9 8 11 10

很經典的一條取數列問題，就是找到一個數列中第m大的數列。

如果使用暴力法就需要O(n!)時間效率，使用特別的方法直接取出數列，那麼時間效率就是O(n)了。

方法就是使用m產生一個取數數列，根據取數數列直接取出d第m大的數，就可以了。

要規範一下函數的介面，形成良好的編程習慣。

網易叫我改投他們的運營，通知明天筆試，我突然間好像說，f you！你運營的能寫出我這麼漂亮的代碼嗎？你運營的需要這麼好的演算法嘛？你運營的需要數十萬行的代碼經驗嗎？

#include <stdio.h>#include <vector>#include <string.h>#include <algorithm>#include <iostream>#include <string>#include <limits.h>#include <stack>#include <queue>#include <set>#include <map>using namespace std;const int MAX_N = 1001;int arr[MAX_N], N, M, tbl[MAX_N], a2[MAX_N];bool genTbl(int tbl[], int n, int m)//n 位， 第m個{--m;if (m < 0) return false;tbl[n-1] = 0;for (int d = 2, i = n-2; i >= 0 ; d++, i--){tbl[i] = m%d;m /= d;}return true;}void eraseElement(int arr[], int i, int *n){(*n)--;for (; i < *n; i++){arr[i] = arr[i+1];}}void getSequence(int res[], int arr[], int tbl[], int n){int i = 0;int *p = arr;while (n){for ( ; n > 0 && tbl[i] == 0; n--, p++, i++){res[i] = *p;}if (!n) return ;res[i] = p[tbl[i]];eraseElement(p, tbl[i], &n);i++;}}int main(){while (~scanf("%d %d", &N, &M)){for (int i = 0; i < N; i++){arr[i] = i+1;}genTbl(tbl, N, M);getSequence(a2, arr, tbl, N);printf("%d", a2[0]);for (int i = 1; i < N; i++){printf(" %d", a2[i]);}putchar('\n');}return 0;}

HDU 1027 取數列問題