JavaScript interesting question: full arrangement and deduplication

Given a string, display all its fully arranged results in the form of an array, requiring no duplicate results.

For example:

I have the string "aabb", and its full permutation result should be 4*3*2*1=24, but considering the requirement that there is no duplication, So the results are 6, as follows:

['aabb', 'abab', 'abba', 'baab', 'baba', 'bbaa']

So the question The key lies in two aspects:

1. How to find the complete arrangement

2. How to deduplicate the results

To find the complete arrangement, you can use either recursive or non-recursive methods .

Deduplication can be achieved using a hash.

//递归求解全排列  
function permutations(string) {  
    //用于存放去重结果的hash  
    var hash = {};  
    //遍历函数  
    //from:要遍历的字符数组  
    //to:记录路径的字符数组  
    var traverse = function(from,to){  
        //若当前深度没有达到叶子  
        if(to.length < string.length){  
            for(var i=0;i<from.length;i++){  
                var newFrom = from.slice(0);  
                var one = newFrom.splice(i,1);  
                var newTo = to.slice(0);  
                newTo = newTo.concat(one);  
                traverse(newFrom,newTo);  
            }  
        }  
        else{  
            //作为key存入hash  
            hash[to.join("")] = null;  
        }  
    };  
      
    traverse(string.split(""),[]);  
    //提取hash的key作为数组返回  
    return Object.keys(hash);  
}

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