[プログラマ]小数を作成(JavaScript)

🔗 質問リンク

📙 私が考えている答えの過程

📝 解答コード

function solution(nums) {
    var answer = 0;
    var tmp = nums.map((val,index)=>index);
    var arr = getCombinations(tmp,3);
    for(var i = 0; i < arr.length; i++){
        var sum = 0;
        for(var j = 0; j < arr[i].length; j++){
            sum += nums[arr[i][j]];
        }
        if(prime(sum))
            answer++;
    }
    return answer;
}
 //조합 알고리즘
function getCombinations(arr, selectNumber) {
	var results = [];
	if (selectNumber === 1) return arr.map((value) => [value]);
	
	arr.forEach((fixed, index, origin) => {
		var rest = origin.slice(index + 1);
		var combinations = getCombinations(rest, selectNumber - 1); 
		var attached = combinations.map((combination) => [fixed, ...combination]);
		results.push(...attached);
	});
	
	return results;
}
//소수면 true 아니면 false 반환하는 함수
function prime(num){
    var cnt = 0;
    if(num > 1){
        for(var i = 1; i <= num; i++){
            if(num%i == 0)
                cnt++;
            if(cnt > 2)
                return false;
        }
        if(cnt <= 2)
            return true;
    }else
        return false;
}