题解 | #24点游戏算法#

import java.util.*;


public class Solution {
    
    public boolean ans = false;

    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * @param nums int整型ArrayList
     * @return bool布尔型
     */
    public boolean Point24(ArrayList<Integer> nums) {
        // write code here
        process(0.0, nums);
        return ans;
    }

    public void process(double previousTotal, ArrayList<Integer> remainNums) {
        if (0 == remainNums.size()) {
            if (previousTotal == (double) 24) {
                ans = true;
            }
            return;
        }
        for (int currentNumber : remainNums) {
            ArrayList<Integer> copyArr = new ArrayList<>(remainNums);
            copyArr.remove(Integer.valueOf(currentNumber));
            process(previousTotal + currentNumber, copyArr);
            process(previousTotal - currentNumber, copyArr);
            process(previousTotal * currentNumber, copyArr);
            process(previousTotal / currentNumber, copyArr);
        }
    }
}