Java实现Djikstra双栈算式解释器, 识别添加优先级

Posted 2020-09-17

package Dijkstra;

import java.util.Stack;
import java.util.regex.*;

/**
 * This class use for get calculate result from the String expression
 * we know that Java language have not class implement method calculate math 
 * expression, javascript have implement "eval".
 * First get simple math expression, iteration wipe out brackets, get expression
 * in brackets and format with priority, then insert result of formative expression 
 * into original expression, and simplify again
 * 
 * Support operator "+", "-", "*", "/", "(", ")", "(-)"
 * use Stack.RegEx
 * 
 * @author Denua
 * @version 07 May 2017 11.48
 */
public class Interpreter {

	public static void main(String[] args) {
		
		String s = "(1+2)-3*5+(5/5*5+5)-1/2";
		Interpreter in = new Interpreter();
		System.out.printf("%s = %g",s,in.elv(s));
	}
	/**
	 * public method as the entry
	 * @param str 
	 * 			String expression
	 * @return
	 * 		double calculate result
	 */
	public double elv(String str){
		
		double res = 0.00;
		res = eval(formate(
				  	 getSimple(str)						
				  )
			  );	
		return res;
	}
	/**
	 * return String simple expression without brackets,use RegEx check brackets and get 
	 * result from the expression in the brackets
	 * @param str 
	 * 			String  complex expression
	 * @return String 
	 * 			String simple expression
	 */
	private String getSimple(String str){
		
		String res = str;
		// RegEx matching the expression in brackets
		Pattern pat2 = Pattern.compile("\\([\\d\\.\\+\\-\\*\\/]+\\)");
		// matching 
		Matcher mat = pat2.matcher(str);
		// if find matching, get simple expression result and joint to origin expression
		if( mat.find() ){
			String find = mat.group(0);
			String st1 = res.substring(0, str.indexOf(find));	
			String st2 = res.substring(str.indexOf(find) + find.length(), res.length());
			
			find = find.substring(1, find.length() - 1);
			find = formate(find);
			find = String.valueOf(eval(find));

			res = st1 + find + st2; 
			// matching again and find expression in brackets, if find, get simple expression
			Matcher mat2 = pat2.matcher(res);
			if(mat2.find()){
				res = getSimple(res);
			}
		}
		return res;
	}
	/**
	 * add brackets for the simple String expression, complete priority, check
	 *  each element in the expression 
	 * 
	 * @param str 
	 * 			String simple  expression
	 * @return String 
	 * 			complete priority expression 
	 */
	private String formate(String str){
		
		String res = str;
		String[][] part = getPart(res);
		String[] pt = new String[part[0].length];
		
		for(int q=0; q < pt.length; q++){
			pt[q] = "";
		}
		
		int count = part[0].length;
		int i = 0;
		
//  all case in priority
//		 (*)	* 	
//		 (+)	+
	 
//		 (*)	+
//		 (+)	*
		
//		 +	*  (*)	+
//		 * (*)	+
		
		while( i < count){

			String id= part[0][i];
			String ir = null;
			if(i < count - 1)
				ir = part[0][i + 1];

			if( nl(id) && nl(ir) ){
				
				if( isf(id) ){
					
					if( isf(ir) ){
						pt[i+1] += ")";
					}
					else if( ! isf(ir) ){
						pt[i+1] += ")";						
						int idx = i - 1;
						
						while( idx >= 0 ){
							String si = part[0][idx];
							if( ! isf(si) ){
								pt[i+1] = "))";
								break;
							}
							idx--;
						}		
					}
				}
				if( ! isf(id) ){
					
					 if( ! isf(ir) )
						pt[i+1] += ")";	
				}				
			}
			else if( nl(id) && ! nl(ir)){
				
				if( isf(id) ){					
					int ix = i - 1;
					boolean find = false;
					
					while( ix >= 0 ){
						String six = part[0][ix];
						if( ! isf(six) ){
							find = true;							
							break;
						}
						ix--;
					}
					if(find)
						part[1][i+1] += "))";
					else
						part[1][i + 1] += ")";
				}
				else
					part[1][i + 1] += ")";
			}
			else{
				return null;
			}						
			i++;
		}
		res = "";
		for(int j = 0; j < part[0].length; j ++){
			part[0][j] = pt[j] + part[0][j];
			res =res + part[1][j] + part[0][j];
		}
		res += part[1][part[1].length -1];
		
		return res;
	}
	/**
	 *  use two Stack calculate expression with complete priority, one Stack
	 *  save number another save operator, check each element in the expression
	 *  with complete priority, if current element is number, then add to 
	 *  number Stack, if operator, add to operator Stack, else is ")" ,  extract
	 *  two number from the number Stack, extract operator from the operator Stack
	 *  and add result to number Stack, iteration get final result.
	 * 
	 * @param str 
	 * 			Complete priority expression
	 * @return double 
	 * 			the result of the expression
	 */
	private Double eval(String str){
		
		Stack<String> operate = new Stack<String>();
		Stack<Double> value = new Stack<Double>();
		
		String[] ele = getEle(str);
		
		int i = 0;
		while( i < ele.length){

			String s = ele[i];
			if(s.equals("(")){
			}
			else if(s.equals("+"))		operate.push(s)	;
			
			else if(s.equals("-"))		operate.push(s) ;

			else if(s.equals("*"))		operate.push(s)	;

			else if(s.equals("/"))		operate.push(s)	;

			else if(s.equals("s"))		operate.push(s)	;

			else if(s.equals(")")){
				
				String op = operate.pop();
				double vl = value.pop();
				
				if(op.equals("+"))			vl = value.pop() + vl;
				
				else if(op.equals("-"))		vl = value.pop() - vl;
				
				else if(op.equals("*"))		vl = value.pop() * vl;
				
				else if(op.equals("/"))		vl = value.pop() / vl;
				
				else if(op.equals("s"))	vl = Math.sqrt(vl);
				
				value.push(vl);
			}
			else{
				value.push(Double.parseDouble(s));
			}			
			i++;
		}
		return value.pop();
	}
	/**
	 * get each part of the expression, cut expression and transform to Array
	 * @param str complete priority expression
	 * @return String[] 
	 */
	private String[] getEle(String str){
		
		Stack<String> st = new Stack<String>();
		
		int j = 0;
		String numbTemp = "";
		while( j < str.length()){
			char temp = str.charAt(j);
			if( isNum(temp) || temp == ‘.‘ || ( j == 0 && temp == ‘-‘) || ( temp == ‘-‘ && isOp(str.charAt(j - 1)) ) ){				
				numbTemp += temp;
			}
			else if( ! isNum(temp)  ){
				if( !numbTemp.isEmpty()){
					st.push(numbTemp);
					numbTemp = "";
				}
				st.push(String.valueOf(temp));
			}
			j++;
		}
		
		String[] res = new String[st.size()];
		for(int i = st.size() - 1; i >= 0; i -- ){
			res[i] = st.pop();
		}
		return res;
	}
	private String[][] getPart(String str){
		
		String res = str;		
		int i = 0;
		Stack<String> cal = new Stack<String>();
		Stack<String> op = new Stack<String>();
		
		String num = "";
		while( i < res.length()){
			char temp = res.charAt(i);			
			if( isOp(temp) ){
				if(temp == ‘-‘ && i == 0)
					num += "-";
				else if( temp == ‘-‘ && isOp(res.charAt(i-1)) )
					num += "-";
				else
					op.push(String.valueOf(temp));
			}
			else if(isNum(temp)){
				num += String.valueOf(temp);
				if(i >= str.length()){
					break;
				}
				else{
					if( i == str.length() - 1){
						
						String n = String.valueOf(str.charAt(i));
						if( isNum(n) && isNum(String.valueOf(str.charAt(i-1)))){
							num += n;
						}
						else{
							num = n;
						}
					}
					else{
						String n = String.valueOf(str.charAt(i + 1));
						boolean flag = true;
						while( isNum(n) && flag){						
							num += n;
							i ++;
							
							if( i > res.length() - 2){
								flag = false;
							}else{
								n = String.valueOf(str.charAt(i + 1));
							}
						}
					}					
				}
				cal.push(num);
				num = "";
			}
			else if(temp == ‘)‘){		
				op.push(")");
			}
			i++;
		}
		i = 0;
		
		String[][] part = new String[2][];
		String[] temp1 = new String[op.size()];
		String[] temp2 = new String[cal.size()];
		for(Object o:op.toArray()){
			temp1[i] = (String) o;
			i++;			
		}
		i = 0;
		for(Object o:cal.toArray()){
			temp2[i] = (String) o;
			i++;			
		}
		
		part[0] = temp1;
		part[1] = temp2;
		
		return part;
		
	}
	private boolean isNum(String str){
		return  str.equals("0") || str.equals("1") || str.equals("2") || str.equals("3") || str.equals("4") ||
				str.equals("5") || str.equals("6") || str.equals("7") || str.equals("8") || str.equals("9") || str.equals(".");
	}
	private boolean isOp(char str){		
		return str == ‘s‘ || str == ‘+‘  ||str == ‘-‘  || str == ‘*‘  || str == ‘/‘ ;
	}
	private boolean isNum(char str){
		return  str == ‘0‘  || str == ‘1‘ || str == ‘2‘  || str == ‘3‘  || str == ‘4‘  ||
				str == ‘5‘  || str == ‘6‘  || str == ‘7‘  || str == ‘8‘  || str == ‘9‘ || str == ‘.‘  ;
	}	
	private boolean isf(String str){
		return str.equals("*") || str.equals("/");
	}
	private boolean nl(Object obj){
		return obj != null;
	}
}