class Solution {
    public boolean judgePoint24(int[] cards) {
        List<Double> list = new ArrayList<>();
        for(int i: cards) {
            list.add((double) i);
        }

        return dfs(list);
    }

    public boolean dfs(List<Double> list) {
        if(list.size() == 1) {
            return Math.abs(list.get(0) - 24) < 1e-8;
        }

        for(int i = 0; i < list.size(); i ++ ) {
            for(int j = 0; j < list.size(); j ++ ) {
                if(i != j) {
                    double a = list.get(i);
                    double b = list.get(j);

                    if(dfs(get(list, i, j, a + b))) return true;
                    if(dfs(get(list, i, j, a - b))) return true;
                    if(dfs(get(list, i, j, a * b))) return true;
                    if(dfs(get(list, i, j, a / b))) return true;
                }
            }
        }

        return false;
    }

    public List<Double> get(List<Double> list, int i, int j, double x) {
        List<Double> res = new ArrayList<>();

        for(int k = 0; k < list.size(); k ++ ) {
            if(k != i && k != j) {
                res.add(list.get(k));
            }
        }

        res.add(x);

        return res;
    }
}