Full array hash - (Cantor Cantor launched expansion and inverse)

Details can be explained with reference to other articles, I have here is reverse Cantor Cantor expansion and deployment JavaScript implementation.

Code:

/ * Full permutation hash - (Cantor Cantor Expand Expand and inverse) 
Cantor Expandable:! X = a [n] * (n-1) + a [n-1] * (n-2) +! A + ... [I] * (I-1)! + ... + A [1] * 0! 
* e.g. 
* is defined as 0 2,3 
* 3,2 is defined as 1 
* 2, 3 is defined as 2 
* 2,3,1 defined as 3 
* 3,1,2 defined as 4 
* 3,2,1 defined as 5 
* * / 

// factorial 
function FAC (X) { 
    the let ANS. 1 = ; 
    for (I = 2 the let; I <= X; I ++) { 
        ANS * = I; 
    } 
    return ANS; 
} 

// Cantor expand: the whole arrangement of a one, it returns an integer representing the ranking of all permutations 
Cantor function (A) { 
    const = n-a.length; 
    the let ANS = 0; 
    for (the let I = 0; I <n-; I ++) { 
        the let TEMP = 0; 
        for (the let = I + J. 1; J <n-; j ++) { 
            IF (A [J] <A [I]) TEMP ++ ; 
        }
        ans += temp * fac(n - i - 1);
    }
    return ans;
}
//逆康托展开
function decantor( x,  oa)
{
    const a=[].concat(oa).sort(function (n,m) {
        return n-m;
    })
    const na=[]
    const n=a.length;
    let temp;
    let used=[];
    let i,j;
    for(i=0;i<n;i++){
        temp= (x/fac(n-i-1))>>0
        for( j=0;j<n;j++){
            if(!used[j]){
                if(temp===0)break;
                --temp;
            }
        }
        na[i]=a[j];
        used[j]=true;
        x=x%fac(n-i-1);
    }
    return na;
}

test:

//测试
const arr1=[5,2,3,4]
for(let i=0;i<fac(arr1.length);i++){
    const arr=decantor(i,arr1);
    console.log(cantor(arr))
    console.log(arr)
}

//结果
"C:\Program Files\nodejs\node.exe" D:\test\Cantor.js
0
[ 2, 3, 4, 5 ]
1
[ 2, 3, 5, 4 ]
2
[ 2, 4, 3, 5 ]
3
[ 2, 4, 5, 3 ]
4
[ 2, 5, 3, 4 ]
5
[ 2, 5, 4, 3 ]
6
[ 3, 2, 4, 5 ]
7
[ 3, 2, 5, 4 ]
8
[ 3, 4, 2, 5 ]
9
[ 3, 4, 5, 2 ]
10
[ 3, 5, 2, 4 ]
11
[ 3, 5, 4, 2 ]
12
[ 4, 2, 3, 5 ]
13
[ 4, 2, 5, 3 ]
14
[ 4, 3, 2, 5 ]
15
[ 4, 3, 5, 2 ]
16
[ 4, 5, 2, 3 ]
17
[ 4, 5, 3, 2 ]
18
[ 5, 2, 3, 4 ]
19
[ 5, 2, 4, 3 ]
20
[ 5, 3, 2, 4 ]
21
[ 5, 3, 4, 2 ]
22
[ 5, 4, 2, 3 ]
23
[ 5, 4, 3, 2 ]

Process finished with exit code 0