String Permutations With No Character Repeats

permAlone.js

function permAlone(str) {
  function factorial(n){
    var f = n;
    for (var i=n-1;i>0;i--){f *= i;}
    return f;
  }
  var fact = factorial(str.length);
  var permuts = [];
  var tmpArr = [];
  var counter = 0;
  var strArr = str.split("");
  (function fillPermutsArr(){
    //console.log("> function");
    for (var p=0;p<strArr.length;p++){
    //console.log("\tstrArr: "+strArr+" | iteration: "+p);
      var zeroIndexChar = strArr.splice(p,1)[0];
      //console.log("\tchar: "+zeroIndexChar+" | strArr, spliced: "+strArr+" | iteration: "+p);
      tmpArr.push(zeroIndexChar);
      //console.log("\ttmpArr, pushed: "+tmpArr+" | iteration: "+p);
      if (strArr.length === 0){
        permuts.push(tmpArr.join().split(","));
        //console.log("=> push permut, permuts: "+JSON.stringify(permuts)+" | iteration: "+p);
      }else{
        //console.log("~ recursion");
        fillPermutsArr();
      }
      //console.log("\tstrArr: "+strArr+" | iteration: "+p);
      strArr.splice(p,0,zeroIndexChar);
      //console.log("\tstrArr, spliced: "+strArr+"| iteration: "+p);
      //console.log("\ttmpArr: "+tmpArr+" | iteration: "+p);
      tmpArr.pop();
      //console.log("\ttmpArr, popped: "+tmpArr+" | iteration: "+p);
      //console.log("~ loop body bottom reached | strArr: "+strArr+" | iteration: "+p);
      if (p == 2){
        //console.log("=> done, permuts: "+JSON.stringify(permuts)+" | iteration: "+p);
      }
    }
  })();
  if (fact == permuts.length){
    for (var q=0;q<permuts.length;q++){
      var letterOccurrenceCounter = 0;
      for (var u=1;u<permuts[q].length;u++){
        if (permuts[q][u-1] == permuts[q][u]){letterOccurrenceCounter++;}
      }
      if (letterOccurrenceCounter === 0){counter++;}
    }
    return counter;
    //return "factorial: "+fact+" | "+"counter: "+counter+" | "+JSON.stringify(permuts);
  }else{
    return "ERROR: factorial and formed permutations array lengths are not equal";
  }
}
permAlone('abc');
//permAlone('aab');
//permAlone("aabb");
//permAlone("abcdefa");
//permAlone("abfdefa");
//permAlone("zzzzzzzz");

StringPermutationsNoCharRepeats.markdown

String Permutations With No Character Repeats

Returns the number of total permutations of the provided string that don't have repeated consecutive letters. In this particular case number of permutations for, for example, 3-character string equals !3 = 3 * 2 * 1 = 6. For example, 'aab' should return 2 because it has 6 total permutations, but only 2 of them don't have the same letter (in this case 'a') repeating.

A script by V.

License.