24点游戏

private static final double E = 0.0001;
    
    public boolean judgePoint24(int[] nums) {
        if (nums == null || nums.length != 4) {
            return false;
        }
        double[] dnums = new double[4];
        for (int i = 0; i < 4; i++) {
            dnums[i] = nums[i];
        }
        return generated24(dnums, 4);
    }
    
    private boolean generated24(double[] nums, int n) {
        if (n == 1) {
            return Math.abs(nums[0] - 24.0) < E;
        }
        for (int i = 0; i < n - 1; i++) {
            double origI = nums[i];
            for (int j = i + 1; j < n; j++) {
                double origJ = nums[j];
                nums[j] = nums[n - 1];
                for (double c : getCombinations(origI, origJ)) {
                    nums[i] = c;
                    if (generated24(nums, n - 1)) {
                        return true;
                    }
                    
                }
                nums[j] = origJ;
            }
            nums[i] = origI;
        }
        return false;
    }
    
    private double[] getCombinations(double a, double b) {
        return new double[]{ a + b, a - b, b - a, a / b, b / a, a * b};
    }
    
}

在这里插入代码片