1 /*************************************************************************
2 > File Name: 45_LastNumberInCircle.cpp
3 > Author: Juntaran
4 > Mail: JuntaranMail@gmail.com
5 > Created Time: 2016年09月04日 星期日 20时21分57秒
6 ************************************************************************/
7
8 #include <stdio.h>
9 #include <bits/stdc++.h>
10
11 using namespace std;
12
13
14 // 环形链表
15 int LastRemaining1(int n, int m)
16 {
17 if (n<1 || m<1)
18 return -1;
19
20 int i = 0;
21
22 list<int> numbers;
23 for (int i = 0; i < n; ++i)
24 numbers.push_back(i);
25
26 list<int>::iterator current = numbers.begin();
27 while (numbers.size() > 1)
28 {
29 for (int i = 1; i < m; ++i)
30 {
31 current ++;
32 if (current == numbers.end())
33 current = numbers.begin();
34 }
35 list<int>::iterator next = ++current;
36 if (next == numbers.end())
37 next = numbers.begin();
38
39 --current;
40 numbers.erase(current);
41 current = next;
42 }
43 return *current;
44 }
45
46 // 数组模拟环
47 int LastRemaining2(int n, int m)
48 {
49 if (n<1 || m<1)
50 return -1;
51
52 int array[n];
53 int i = -1;
54 int step = 0;
55 int count = n;
56
57 while (count > 0)
58 {
59 i ++;
60 if (i >= n) // 模拟环
61 i = 0;
62 if (array[i] == -1)
63 continue;
64 step ++;
65 if (step == m)
66 {
67 array[i] = -1;
68 step = 0;
69 count --;
70 }
71 }
72 int ret = i;
73 return ret;
74 }
75
76 // 数学解法
77 int LastRemaining3(int n, int m)
78 {
79 if (n<1 || m<1)
80 return -1;
81
82 int ret = 0;
83 for (int i = 2; i <= n; ++i)
84 ret = (ret + m) % i;
85
86 return ret;
87 }
88
89 int main()
90 {
91 int n = 100;
92 int m = 5;
93
94 int ret1 = LastRemaining1(n, m);
95 int ret2 = LastRemaining2(n, m);
96 int ret3 = LastRemaining3(n, m);
97
98 printf("ret1 is %d\n", ret1);
99 printf("ret2 is %d\n", ret2);
100 printf("ret3 is %d\n", ret3);
101
102 return 0;
103 }
