forked from haoel/leetcode
-
Notifications
You must be signed in to change notification settings - Fork 0
Expand file tree
/
Copy pathpermutations.cpp
More file actions
112 lines (101 loc) · 2.48 KB
/
Copy pathpermutations.cpp
File metadata and controls
112 lines (101 loc) · 2.48 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
// Source : https://oj.leetcode.com/problems/permutations/
// Author : Hao Chen
// Date : 2014-06-21
/**********************************************************************************
*
* Given a collection of numbers, return all possible permutations.
*
* For example,
* [1,2,3] have the following permutations:
* [1,2,3], [1,3,2], [2,1,3], [2,3,1], [3,1,2], and [3,2,1].
*
*
**********************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <iostream>
#include <vector>
using namespace std;
/*
{ 1 2 3 }
{ 2 1 3 }
{ 3 2 1 }
{ 1 3 2 }
{ 2 3 1 }
{ 3 1 2 }
*/
/*
* The algroithm - Take each element in array to the first place.
*
* For example:
*
* 0) initalization
*
* pos = 0
* [1, 2, 3]
*
* 1) take each element into the first place,
*
* pos = 1
* [1, 2, 3] ==> [2, 1, 3] , [3, 1, 2]
*
* then we have total 3 answers
* [1, 2, 3], [2, 1, 3] , [3, 1, 2]
*
* 2) take each element into the "first place" -- pos
*
* pos = 2
* [1, 2, 3] ==> [1, 3, 2]
* [2, 1, 3] ==> [2, 3, 1]
* [3, 1, 2] ==> [3, 2, 1]
*
* then we have total 6 answers
* [1, 2, 3], [2, 1, 3] , [3, 1, 2], [1, 3, 2], [2, 3, 1], [3, 2, 1]
*
* 3) pos = 3 which greater than length of array, return.
*
*/
vector<vector<int> > permute(vector<int> &num) {
vector<vector<int> > vv;
vv.push_back(num);
if (num.size() <2){
return vv;
}
int pos=0;
while(pos<num.size()-1){
int size = vv.size();
for(int i=0; i<size; i++){
//take each number to the first place
for (int j=pos+1; j<vv[i].size(); j++) {
vector<int> v = vv[i];
int t = v[j];
v[j] = v[pos];
v[pos] = t;
vv.push_back(v);
}
}
pos++;
}
return vv;
}
int main(int argc, char** argv)
{
int n = 3;
if (argc>1){
n = atoi(argv[1]);
}
vector<int> v;
for (int i=0; i<n; i++) {
v.push_back(i+1);
}
vector<vector<int> > vv;
vv = permute(v);
for(int i=0; i<vv.size(); i++) {
cout << "{ ";
for(int j=0; j<vv[i].size(); j++){
cout << vv[i][j] << " ";
}
cout << "}" <<endl;
}
return 0;
}