Example of the arrangement and combination problem implemented by Go language (m out of n numbers)

package huawei
import (
    "fmt"
    "time"
)
/*
[Arrangement and combination problem: Take m of n numbers]
*/
func Test10Base() {
    nums := []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
    m := 5
    timeStart := ()
    n := len(nums)
    indexs := zuheResult(n, m)
    result := findNumsByIndexs(nums, indexs)
    timeEnd := ()
    ("count:", len(result))
    ("result:", result)
    ("time consume:", (timeStart))
//Is the result correct
    rightCount := mathZuhe(n, m)
    if rightCount == len(result) {
("Result is correct")
    } else {
("The result is wrong, the correct result is:", rightCount)
    }
}
//Combination algorithm (take out m numbers from nums)
func zuheResult(n int, m int) [][]int {
    if m < 1 || m > n {
        ("Illegal argument. Param m must between 1 and len(nums).")
        return [][]int{}
    }
//Save the array of final results, and the total number is calculated directly through mathematical formulas
    result := make([][]int, 0, mathZuhe(n, m))
//Save the array of indexes for each combination, 1 means selected, 0 means unselected
    indexs := make([]int, n)
    for i := 0; i < n; i++ {
        if i < m {
            indexs[i] = 1
        } else {
            indexs[i] = 0
        }
    }
//The first result
    result = addTo(result, indexs)
    for {
        find := false
//Each cycle changes the first occurrence of 1 0 to 0 1, and move the left 1 to the leftmost
        for i := 0; i < n-1; i++ {
            if indexs[i] == 1 && indexs[i+1] == 0 {
                find = true
                indexs[i], indexs[i+1] = 0, 1
                if i > 1 {
                    moveOneToLeft(indexs[:i])
                }
                result = addTo(result, indexs)
                break
            }
        }
//There is no 1 0 found in this loop, which means that the last situation has been obtained
        if !find {
            break
        }
    }
    return result
}
//Copy ele and add it to arr and return a new array
func addTo(arr [][]int, ele []int) [][]int {
    newEle := make([]int, len(ele))
    copy(newEle, ele)
    arr = append(arr, newEle)
    return arr
}
func moveOneToLeft(leftNums []int) {
//How many 1s are calculated
    sum := 0
    for i := 0; i < len(leftNums); i++ {
        if leftNums[i] == 1 {
            sum++
        }
    }
//Change the first sum to 1, and then change the next sum to 0
    for i := 0; i < len(leftNums); i++ {
        if i < sum {
            leftNums[i] = 1
        } else {
            leftNums[i] = 0
        }
    }
}
//Get an array of elements based on the index number array
func findNumsByIndexs(nums []int, indexs [][]int) [][]int {
    if len(indexs) == 0 {
        return [][]int{}
    }
    result := make([][]int, len(indexs))
    for i, v := range indexs {
        line := make([]int, 0)
        for j, v2 := range v {
            if v2 == 1 {
                line = append(line, nums[j])
            }
        }
        result[i] = line
    }
    return result
}

//Mathematical method calculates the number of arrangements (take m numbers from n)
func mathPailie(n int, m int) int {
    return jieCheng(n) / jieCheng(n-m)
}
//Mathematical method calculates the combined number (take m numbers from n)
func mathZuhe(n int, m int) int {
    return jieCheng(n) / (jieCheng(n-m) * jieCheng(m))
}
//factorial
func jieCheng(n int) int {
    result := 1
    for i := 2; i <= n; i++ {
        result *= i
    }
    return result
}

func pailieResult(nums []int, m int) [][]int {
//Combination results
    zuhe := zuheResult(nums, m)
//Save the final arrangement result
    result := make([][]int, 0)
//Transfer the combination results and arrange each item in full
    for _, v := range zuhe {
        p := quanPailie(v)
        result = append(result, p...)
    }
    return result
}
//N numbers are arranged
//If you enter [1 2 3], return [123 132 213 231 312 321]
func quanPailie(nums []int) [][]int {
    COUNT := len(nums)
//examine
    if COUNT == 0 || COUNT > 10 {
        panic("Illegal argument. nums size must between 1 and 9.")
    }
//If there is only one number, return directly
    if COUNT == 1 {
        return [][]int{nums}
    }
// Otherwise, insert the last number into all positions in the previous arrangement number
    return insertItem(quanPailie(nums[:COUNT-1]), nums[COUNT-1])
}
func insertItem(res [][]int, insertNum int) [][]int {
//Save the slice of the result
    result := make([][]int, len(res)*(len(res[0])+1))
    index := 0
    for _, v := range res {
        for i := 0; i < len(v); i++ {
//Insert new element in front of each element of v
            result[index] = insertToSlice(v, i, insertNum)
            index++
        }
//Insert new element at the end of v
        result[index] = append(v, insertNum)
        index++
    }
    return result
}
//Insert the element value into the position in the array nums index
func insertToSlice(nums []int, index int, value int) []int {
    result := make([]int, len(nums)+1)
    copy(result[:index], nums[:index])
    result[index] = value
    copy(result[index+1:], nums[index:])
    return result
}