# Full permutation implementation of Golang permutation algorithm problem

• 2020-06-01 10:01:33
• OfStack

In this paper, an example of Golang permutation algorithm is presented. I will share it with you for your reference as follows:

[permutation and combination problem]

1 altogether N trains (0 < N < 10), each train is numbered 1-9, and the train's outbound serial number is required to be output in lexicographical order.

Input:

Including N positive integers (0) < N < 10), which ranges from 1 to 9. The Numbers are separated by Spaces. The first part of the string does not contain Spaces.

Output:

Output the lexicographical train outbound sequence number, each number separated by a space, each output sequence line feed.

Sample input:

1 2 3

Sample output:

1 2 3
1 3 2
2 1 3
2 3 1
3 1 2
3 2 1

Code implementation:

``````package huawei
import (
"fmt"
"sort"
"strings"
)
func Test7Base() {
in := "5 2 3"
result := outOrder(strings.Fields(in))
dictSort(result)
s := format(result)
fmt.Println(s)
}
// The input trainsNums , returns all permutations
// Such as the input [1 2 3] , the return [123 132 213 231 312 321]
func outOrder(trainsNums []string) []string {
COUNT := len(trainsNums)
// check
if COUNT == 0 || COUNT > 10 {
panic("Illegal argument. trainsNums size must between 1 and 9.")
}
// If only 1 The number is directly returned
if COUNT == 1 {
return []string{trainsNums}
}
// Otherwise, it will be the last 1 Number inserted into all positions in the preceding permutation number (recursion)
return insert(outOrder(trainsNums[:COUNT-1]), trainsNums[COUNT-1])
}
func insert(res []string, insertNum string) []string {
// Save the result slice
result := make([]string, len(res)*(len(res)+1))
index := 0
for _, v := range res {
for i := 0; i < len(v); i++ {
// in v Each of the 1 Two elements are inserted in front of each other
result[index] = v[:i] + insertNum + v[i:]
index++
}
// in v Backmost insertion
result[index] = v + insertNum
index++
}
return result
}
// Sort in lexicographical order
func dictSort(res []string) {
sort.Strings(res)
}
// Output in the specified format
func format(res []string) string {
strs := make([]string, len(res))
for i := 0; i < len(res); i++ {
}
return strings.Join(strs, "\n")
}
var retVal string
for i := 0; i < len(s); i++ {
retVal += string(s[i])
if i != len(s)-1 {
retVal += " "
}
}
return retVal
}``````