【算法】程序猿不写代码是不对的14

package com.kingdz.algorithm.time201702;import java.util.HashMap;import java.util.HashSet;import java.util.List;import java.util.Map;import java.util.Set;/** * 算数表达式求值<br/> * 求解思路：按照计算表达式的思考模式，从左到右一次计算，判断每个运算符前后两个临近运算符的优先级来判断计算的方式<br/> * 缺陷：目前在处理中括号和大括号时会有困难 *  * @author kingdz *  */public class Algo08 {	// 优先级map	public static final Map<String, Integer> PRiorMap;	static {		priorMap = new HashMap<String, Integer>();		priorMap.put("+", 0);		priorMap.put("-", 0);		//		priorMap.put("*", 1);		priorMap.put("/", 1);		//		priorMap.put("(", 2);		priorMap.put(")", 2);		//		priorMap.put("[", 3);		priorMap.put("]", 3);		//		priorMap.put("{", 4);		priorMap.put("}", 4);	}	public static void main(String[] args) {		String question = "1+2*(3+4)*5-6";		// 将字符串转化为list		List<String> list = Algo07.dismantle(question);		System.out.print(" ");		// 首先打印需要计算的结果		printList(list, false);		int result = cal(list);		// 输出最终计算的结果		System.out.println(result);	}	/**	 * 打印list，类似于算术	 * 	 * @param list	 * @param isPrintEquals	 *            是否在前面打印“=”符号	 */	private static void printList(List<String> list, boolean isPrintEquals) {		StringBuilder strb = new StringBuilder();		for (String str : list) {			strb.append(str);		}		if (isPrintEquals) {			System.out.println("=" + strb);		} else {			System.out.println(strb);		}	}	/**	 * 打印list，类似于算术	 * 	 * @param list	 */	private static void printList(List<String> list) {		printList(list, true);	}	/**	 * 计算list表达式	 * 	 * @param list	 * @return	 */	private static int cal(List<String> list) {		// 将所有运算符存入set，方便判断是否是运算符		Set<String> set = new HashSet<String>();		for (String str : Algo07.separator) {			set.add(str);		}		// 用于标记当前处理的位置		int index = 0;		// 当list的大小为1时表示计算完成		while (list.size() > 1) {			if (index >= list.size()) {				// 如果已经处理到结尾，但是依然没有计算出结果则重新计算				index = 0;			}			// 获得当前处理的字符串			String now = list.get(index);			{				String before2 = index - 2 >= 0 ? list.get(index - 2) : null;				String before1 = index - 1 >= 0 ? list.get(index - 1) : null;				String after1 = index + 1 < list.size() ? list.get(index + 1) : null;				String after2 = index + 2 < list.size() ? list.get(index + 2) : null;				if (before1 != null && after1 != null) {					{						// 用于去括号						boolean accord = false;						if (before1.equals("(") && after1.equals(")")) {							accord = true;						} else if (before1.equals("[") && after1.equals("]")) {							accord = true;						} else if (before1.equals("{") && after1.equals("}")) {							accord = true;						}						if (accord) {							list.remove(index + 1);							list.remove(index - 1);							// index--;							index = 0;							// System.out.println(list);							printList(list);							continue;						}					}					// 是运算符					if (set.contains(now)) {						// 计算前后的优先级						int beforePrior2 = getPriority(before2);						// int beforePrior1 = getPriority(before1);						int nowPrior = getPriority(now);						// int afterPrior1 = getPriority(after1);						int afterPrior2 = getPriority(after2);						if (nowPrior == 1 || (nowPrior == 0 && beforePrior2 != 1 && afterPrior2 != 1)) {							int beforeInt;							int afterInt;							try {								beforeInt = Integer.parseInt(list.get(index - 1));								afterInt = Integer.parseInt(list.get(index + 1));							} catch (NumberFormatException e) {								index++;								continue;							}							// 实际进行计算处理							boolean accord = false;							if ("+".equals(now)) {								list.set(index, "" + (beforeInt + afterInt));								accord = true;							} else if ("-".equals(now)) {								list.set(index, "" + (beforeInt - afterInt));								accord = true;							} else if ("*".equals(now)) {								list.set(index, "" + (beforeInt * afterInt));								accord = true;							} else if ("/".equals(now)) {								list.set(index, "" + (beforeInt / afterInt));								accord = true;							}							if (accord) {								list.remove(index + 1);								list.remove(index - 1);								// index--;								index = 0;								// System.out.println(list);								printList(list);								continue;							}						}					}				}			}			index++;		}		return Integer.parseInt(list.get(0));	}	/**	 * 根据运算符判断优先级数字	 * 	 * @param str	 * @return 如果是空则返回-1，如果没有则返回-2	 * 	 */	private static int getPriority(String str) {		if (str == null) {			return -1;		}		if (priorMap.containsKey(str)) {			return priorMap.get(str);		} else {			return -2;		}	}}