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@ -1,127 +0,0 @@
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package Stack;
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import java.util.ArrayList;
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import java.util.List;
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import java.util.Stack;
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public class Calculation{
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//将中缀表达式转为List
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public static List<String> InfixtoList(String s){
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List<String> l=new ArrayList<String>();
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int i=0;//用于遍历中缀表达式字符串
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String splicing;//对多位数的拼接
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char c;//遍历每一个字符,就被列入c
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do {//如果c是非数字,就加入到l中
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if((c=s.charAt(i))<48||(c=s.charAt(i))>57) {
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l.add(""+c);
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i++;
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}else {//如果是一个数还需要考虑多位数的问题
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splicing="";//先见str置成""
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while(i<s.length() && (c=s.charAt(i))>=48 && (c=s.charAt(i))<=57) {
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splicing+=c;
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i++;
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}
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l.add(splicing);
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}
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}while(i<s.length());
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return l;
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}
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//将得到List转为后缀表达式
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public static List<String> ListtoSuffix(List<String> l){
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Stack<String> s1=new Stack<String> ();
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List<String> s2=new ArrayList<String> ();
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//遍历l
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for(String item: l) {
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//如果是一个数则加入到s2
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if(item.matches("\\d+"))
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{
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s2.add(item);
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}else if(item.equals("(")){
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s1.push(item);
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}else if(item.equals(")")){
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while(!s1.peek().equals("(")) {//查看s1中的元素是否等于(
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s2.add(s1.pop());
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}
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s1.pop();//将(弹出,消除(
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}else {
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//当item的优先级小于等于栈顶的优先级将s1栈顶运算符弹出压入到s2中,再次与s1中的栈顶运算符比较
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while(s1.size()!=0 && Operation.getValue(s1.peek())>=Operation.getValue(item)) {
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s2.add(s1.pop());
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}
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//还需要将item压入栈中
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s1.push(item);
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}
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}
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while(s1.size()!=0) {
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s2.add(s1.pop());
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}
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return s2;
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}
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//计算
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public static int calculate(List<String> l) {
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//创建一个栈
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Stack<String> stack=new Stack<String>();
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for(String item: l) {
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if(item.matches("\\d+")) {//匹配的是多位数
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stack.push(item);
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}
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else {
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int num2=Integer.parseInt(stack.pop());
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int num1=Integer.parseInt(stack.pop());
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int res=0;
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if(item.equals("+")) {
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res=num1+num2;
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}else if(item.equals("-")) {
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res=num1-num2;
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}else if(item.equals("*")) {
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res=num1*num2;
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}else if(item.equals("/")) {
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res=num1/num2;
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}else {
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throw new RuntimeException("运算符有误");
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}
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//把res入栈
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stack.push(res+"");//把整数转为字符串
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}
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}
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//最后留在stack中的数据就是运算结果
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return Integer.parseInt(stack.pop());
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}
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}
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//编写一个类Operation可以返回一个运算符对应的优先级
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class Operation{
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private static int ADD=1;
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private static int SUB=1;
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private static int MUL=2;
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private static int DIV=2;
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//写一个方法返回对应的优先级
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public static int getValue(String operation) {
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int result=0;
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switch (operation) {
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case "+":
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result=ADD;
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break;
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case "-":
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result=SUB;
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break;
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case "*":
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result=MUL;
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break;
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case "/":
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result=DIV;
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break;
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default:
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//System.out.println("不存在该运算符");
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break;
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}
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return result;
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}
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}
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