iPad游戏 Calcculator: The Game 程序自动计算求解方法

package com;

import com.google.common.collect.Lists;

import java.util.ArrayDeque;
import java.util.Deque;
import java.util.List;

/**
 * 2018-08-24 下午10:36.
 *
 * @Author yangliqun
 */
public class Calc {
    public static void main(String[] args) {
        int n = 5;
        int start = 0;
        int target = 210;
        List<Num> list = Lists.newArrayList();
        list.add(new Num(OpType.SET, 2));
        list.add(new Num(OpType.SET, 5));
//        list.add(new Num(OpType.LEFT_SHIFT, 0));
        list.add(new Num(OpType.ADD, 5));
        list.add(new Num(OpType.SUB, 5));
//        list.add(new Num(OpType.SET, 0));
//        list.add(new Num(OpType.SET, 5));
        dfs(list, new ArrayDeque<>(), n, start, target);
    }

    static void dfs(List<Num> list, Deque<Num> res, int step, int last, int target) {
        if (list == null || list.size() == 0 || step <= 0) {
            return;
        }
        for (int i = 0; i < list.size(); i++) {
            Num num = list.get(i);
            int tmp = num.calc(last);
            if (tmp == 0xdeadbeef) {
                continue;
            }
            res.offer(num);
            if (tmp == target) {
                System.out.println(res);
            } else {
                dfs(list, res, step - 1, tmp, target);
            }
            res.pollLast();
        }
    }

    static class Num {
        OpType opType;
        int num;

        protected Num(OpType opType, int num) {
            this.opType = opType;
            this.num = num;
        }

        public int calc(int last) {
            if (this.opType == OpType.SET) {
                if (last == 0) {
                    return this.num;
                } else {
                    return last * (int)Math.pow(10, this.num / 10 + 1) + this.num;
                }
            }
            if (this.opType == OpType.LEFT_SHIFT) {
                return last / 10;
            }
            if (this.opType == OpType.ADD) {
                return this.num + last;
            }
            if (this.opType == OpType.SUB) {
                return last - this.num;
            }
            if (this.opType == OpType.MUL) {
                return last * this.num;
            } else {
                if (last % this.num == 0) {
                    return last / this.num;
                } else {
                    return 0xdeadbeef;
                }
            }
        }

        @Override
        public String toString() {
            return "Num{" +
                    "opType=" + opType +
                    ", num=" + num +
                    ‘}‘;
        }
    }

    enum OpType {
        SET, ADD, SUB, MUL, DIV, LEFT_SHIFT;
    }
}