题目如下：

解题方法：

var arr = new Array(10).fill("A");    var flag = true ;    run(); // ["B", "C", "A", "C", "A", "C", "D", "A", "B", "A"]    function run () {        try {            if(flag){                flag = false ;                recursion() ;            }        } catch (err) {            flag = true;            run();        }    }        function a1 (){        return true;    }    function a2 (){        switch(arr[1])        {        case "A":            return arr[4] === "C"        case "B":            return arr[4] === "D"        case "C":            return arr[4] === "A"        case "D":            return arr[4] === "B"        default:            return false;        }    }    function a3 (){        switch(arr[2])        {        case "A":            return arr[5] === arr[1] && arr[5] === arr[3]        case "B":            return arr[2] === arr[1] && arr[2] === arr[3]        case "C":            return arr[5] === arr[2] && arr[5] === arr[3]        case "D":            return arr[5] === arr[1] && arr[5] === arr[2]        default:            return false;        }    }    function a4 (){        var f1 = arr[0] === arr[4] ,            f2 = arr[1] === arr[6] ,            f3 = arr[0] === arr[8] ,            f4 = arr[5] === arr[9] ;        switch(arr[3])        {        case "A":            return f1 && !f2 && !f3 && !f4        case "B":            return !f1 && f2 && !f3 && !f4        case "C":            return !f1 && !f2 && f3 && !f4        case "D":            return !f1 && !f2 && !f3 && f4        default:            return false;        }    }    function a5 (){        switch(arr[4])        {        case "A":            return arr[7] === "A"        case "B":            return arr[3] === "B"        case "C":            return arr[8] === "C"        case "D":            return arr[6] === "D"        default:            return false;        }    }    function a6 (){        var f1 = arr[7] === arr[1] && arr[7] === arr[3] ,            f2 = arr[7] === arr[0] && arr[7] === arr[5] ,            f3 = arr[7] === arr[2] && arr[7] === arr[9] ,            f4 = arr[7] === arr[4] && arr[7] === arr[8] ;        switch(arr[5])        {        case "A":            return f1 && !f2 && !f3 && !f4        case "B":            return !f1 && f2 && !f3 && !f4        case "C":            return !f1 && !f2 && f3 && !f4        case "D":            return !f1 && !f2 && !f3 && f4        default:            return false;        }    }    function a7 (){        var c1 = arr.filter((i)=>{
   return i === "A"}).length ,            c2 = arr.filter((i)=>{
   return i === "B"}).length ,            c3 = arr.filter((i)=>{
   return i === "C"}).length ,            c4 = arr.filter((i)=>{
   return i === "D"}).length ;        switch(arr[6])        {        case "A":            return Math.min(c1,c2,c3,c4) === c3        case "B":            return Math.min(c1,c2,c3,c4) === c2        case "C":            return Math.min(c1,c2,c3,c4) === c1        case "D":            return Math.min(c1,c2,c3,c4) === c4        default:            return false;        }    }    function a8 (){        switch(arr[7])        {        case "A":            return Math.abs(arr[0].charCodeAt(0) - arr[6].charCodeAt(0))>=2        case "B":            return Math.abs(arr[0].charCodeAt(0) - arr[4].charCodeAt(0))>=2        case "C":            return Math.abs(arr[0].charCodeAt(0) - arr[1].charCodeAt(0))>=2        case "D":            return Math.abs(arr[0].charCodeAt(0) - arr[9].charCodeAt(0))>=2        default:            return false;        }    }    function a9 (){        var flag = arr[0] === arr[5],            f1 = (arr[4] === arr[5]) === !flag ,            f2 = (arr[4] === arr[9]) === !flag ,            f3 = (arr[4] === arr[1]) === !flag ,            f4 = (arr[4] === arr[8]) === !flag ;        switch(arr[8])        {        case "A":            return f1 && !f2 && !f3 && !f4        case "B":            return !f1 && f2 && !f3 && !f4        case "C":            return !f1 && !f2 && f3 && !f4        case "D":            return !f1 && !f2 && !f3 && f4        default:            return false;        }    }    function a10 (){        var c1 = arr.filter((i)=>{
   return i === "A"}).length ,            c2 = arr.filter((i)=>{
   return i === "B"}).length ,            c3 = arr.filter((i)=>{
   return i === "C"}).length ,            c4 = arr.filter((i)=>{
   return i === "D"}).length ;        switch(arr[9])        {        case "A":            return Math.max(c1,c2,c3,c4) - Math.min(c1,c2,c3,c4) === 3        case "B":            return Math.max(c1,c2,c3,c4) - Math.min(c1,c2,c3,c4) === 2        case "C":            return Math.max(c1,c2,c3,c4) - Math.min(c1,c2,c3,c4) === 4        case "D":            return Math.max(c1,c2,c3,c4) - Math.min(c1,c2,c3,c4) === 1        default:            return false;        }    }    function vali () {        return a1() && a2() && a3() && a4() && a5() && a6() && a7() && a8() && a9() && a10() ;    }        //递归遍历arr的所有排列组合    function recursion (){        if(vali()){            console.log(arr);        }        for(var x=0 ; x