Possible solution to Rosetta Code Challenge - 24 game

What is your hint or solution suggestion?

Solution
function solve24 (numStr) {

  let init_arr = numStr.split('');

  let perm_arr = [init_arr];

  for(let e = 0; e < 23; e++) {

    // using the algorith from page 142 - https://homepage.math.uiowa.edu/~goodman/22m150.dir/2007/Permutation%20Generation%20Methods.pdf

    if(e % 2 === 0) [init_arr[0], init_arr[1]] = [init_arr[1], init_arr[0]];

    else if(e % 2 !== 0) {

      if(e === 5 || e === 11) [init_arr[2], init_arr[3]] = [init_arr[3], init_arr[2]];

      else if(e === 17) {

        [init_arr[0], init_arr[3]] = [init_arr[3], init_arr[0]];

        [init_arr[1], init_arr[2]] = [init_arr[2], init_arr[1]];

      } else {

        [init_arr[1], init_arr[2]] = [init_arr[2], init_arr[1]];

      }

    }

    perm_arr.push(Array.from(init_arr));

  };

  for(let e = 0; e < perm_arr.length; e++) {

    // probably these aren't all the possible formulas

    let formulas = [

      `(${perm_arr[e][0]}-${perm_arr[e][1]}/${perm_arr[e][2]})*${perm_arr[e][3]}`,

      `${perm_arr[e][0]}*${perm_arr[e][1]}*${perm_arr[e][2]}*${perm_arr[e][3]}`, 

      `(${perm_arr[e][0]}*${perm_arr[e][1]})/(${perm_arr[e][2]}-${perm_arr[e][3]})`,

      `(${perm_arr[e][3]}+${perm_arr[e][2]})*(${perm_arr[e][1]}+${perm_arr[e][0]})`,

      

      `${perm_arr[e][0]}+${perm_arr[e][1]}+${perm_arr[e][2]}+${perm_arr[e][3]}`,

      `${perm_arr[e][0]}+${perm_arr[e][1]}+${perm_arr[e][2]}-${perm_arr[e][3]}`,

      `${perm_arr[e][0]}*${perm_arr[e][1]}*${perm_arr[e][2]}/${perm_arr[e][3]}`,  

      `${perm_arr[e][0]}*${perm_arr[e][1]}+${perm_arr[e][2]}/${perm_arr[e][3]}`,  

      `${perm_arr[e][0]}*${perm_arr[e][1]}-${perm_arr[e][2]}/${perm_arr[e][3]}`,  

      `${perm_arr[e][0]}*${perm_arr[e][1]}*${perm_arr[e][2]}+${perm_arr[e][3]}`,  

      `${perm_arr[e][0]}*${perm_arr[e][1]}*${perm_arr[e][2]}-${perm_arr[e][3]}`,  

      `${perm_arr[e][0]}*${perm_arr[e][1]}+${perm_arr[e][2]}+${perm_arr[e][3]}`,  

      `${perm_arr[e][0]}*${perm_arr[e][1]}+${perm_arr[e][2]}-${perm_arr[e][3]}`, 

      `${perm_arr[e][0]}*${perm_arr[e][1]}-${perm_arr[e][2]}-${perm_arr[e][3]}`, 

      `${perm_arr[e][0]}*${perm_arr[e][1]}+${perm_arr[e][2]}*${perm_arr[e][3]}`,  

      `${perm_arr[e][0]}*${perm_arr[e][1]}-${perm_arr[e][2]}*${perm_arr[e][3]}`,  

      `${perm_arr[e][0]}*${perm_arr[e][1]}+${perm_arr[e][2]}/${perm_arr[e][3]}`,  

      `${perm_arr[e][0]}*${perm_arr[e][1]}-${perm_arr[e][2]}/${perm_arr[e][3]}`,  

      `(${perm_arr[e][0]}+${perm_arr[e][1]})*(${perm_arr[e][2]}-${perm_arr[e][3]})`,

      `(${perm_arr[e][0]}-${perm_arr[e][1]})*(${perm_arr[e][2]}+${perm_arr[e][3]})`,

      `(${perm_arr[e][0]}-${perm_arr[e][1]})*(${perm_arr[e][2]}-${perm_arr[e][3]})`,

      `(${perm_arr[e][0]}+${perm_arr[e][1]})/(${perm_arr[e][2]}+${perm_arr[e][3]})`,

      `(${perm_arr[e][0]}+${perm_arr[e][1]})/(${perm_arr[e][2]}-${perm_arr[e][3]})`,

      `(${perm_arr[e][0]}-${perm_arr[e][1]})/(${perm_arr[e][2]}+${perm_arr[e][3]})`,

      `(${perm_arr[e][0]}-${perm_arr[e][1]})/(${perm_arr[e][2]}-${perm_arr[e][3]})`,

      `(${perm_arr[e][0]}*${perm_arr[e][1]})/(${perm_arr[e][2]}+${perm_arr[e][3]})`,

      `${perm_arr[e][0]}*(${perm_arr[e][1]}+${perm_arr[e][2]}+${perm_arr[e][3]})`,

      `${perm_arr[e][0]}*(${perm_arr[e][1]}+${perm_arr[e][2]}-${perm_arr[e][3]})`,

      `${perm_arr[e][0]}*(${perm_arr[e][1]}-${perm_arr[e][2]}-${perm_arr[e][3]})`,

      `${perm_arr[e][0]}*(${perm_arr[e][1]}*${perm_arr[e][2]}*${perm_arr[e][3]})`,

      `${perm_arr[e][0]}*(${perm_arr[e][1]}/${perm_arr[e][2]}*${perm_arr[e][3]})`,

      `${perm_arr[e][0]}*(${perm_arr[e][1]}+${perm_arr[e][2]}*${perm_arr[e][3]})`,

      `${perm_arr[e][0]}*(${perm_arr[e][1]}-${perm_arr[e][2]}*${perm_arr[e][3]})`,

      `${perm_arr[e][0]}*(${perm_arr[e][1]}+${perm_arr[e][2]}/${perm_arr[e][3]})`,

      `${perm_arr[e][0]}*(${perm_arr[e][1]}-${perm_arr[e][2]}/${perm_arr[e][3]})`,      

      `${perm_arr[e][0]}/(${perm_arr[e][1]}*${perm_arr[e][2]}*${perm_arr[e][3]})`,

      `${perm_arr[e][0]}/(${perm_arr[e][1]}/${perm_arr[e][2]}*${perm_arr[e][3]})`,

      `${perm_arr[e][0]}/(${perm_arr[e][1]}+${perm_arr[e][2]}*${perm_arr[e][3]})`,

      `${perm_arr[e][0]}/(${perm_arr[e][1]}-${perm_arr[e][2]}*${perm_arr[e][3]})`,

      `${perm_arr[e][0]}/(${perm_arr[e][1]}+${perm_arr[e][2]}/${perm_arr[e][3]})`,

      `${perm_arr[e][0]}/(${perm_arr[e][1]}-${perm_arr[e][2]}/${perm_arr[e][3]})`,

      `${perm_arr[e][0]}*(${perm_arr[e][1]}-${perm_arr[e][2]}/${perm_arr[e][3]})`,

      `(${perm_arr[e][0]}+${perm_arr[e][1]}) * ${perm_arr[e][2]}+${perm_arr[e][3]}`,

      `(${perm_arr[e][0]}+${perm_arr[e][1]}) * ${perm_arr[e][2]}-${perm_arr[e][3]}`,

      `(${perm_arr[e][0]}-${perm_arr[e][1]}) * ${perm_arr[e][2]}+${perm_arr[e][3]}`,

      `(${perm_arr[e][0]}-${perm_arr[e][1]}) * ${perm_arr[e][2]}-${perm_arr[e][3]}`,

      `(${perm_arr[e][0]}+${perm_arr[e][1]}) * ${perm_arr[e][2]}*${perm_arr[e][3]}`,

      `(${perm_arr[e][0]}+${perm_arr[e][1]}) * ${perm_arr[e][2]}/${perm_arr[e][3]}`,

      `(${perm_arr[e][0]}+${perm_arr[e][1]}) / ${perm_arr[e][2]}*${perm_arr[e][3]}`,

    ];

    for(let i = 0; i < formulas.length; i++) {

      if(eval(formulas[i]) === 24) return formulas[i];

    }

  }

}
console.log(solve24("4878")) ;

Challenge: 24 game

Link to the challenge:

Hi @alex.songureanu74 !

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