package com.interview.flag.f;
import com.interview.basics.model.collection.hash.HashSet;
import java.util.Stack;
/**
* Created_By: stefanie
* Date: 14-12-10
* Time: 上午11:03
*/
public class F5_SimplifyExpression {
static String ONLYNUMBERS = "[0-9]*";
static HashSet<String> operators = new HashSet<>();
static {
operators.add("+");
operators.add("-");
operators.add("*");
operators.add("/");
}
//x 1 + 3 * 2 2x 5 + * + -> 7x + 13
public String simplify(String[] expression){
Stack<String> stack = new Stack<>();
for(int i = 0; i < expression.length; i++){
String variable = expression[i];
if(operators.contains(variable)){
String second = stack.pop();
String first = stack.pop();
String result = calculate(first, second, variable);
stack.push(result);
} else {
stack.push(variable);
}
}
return stack.pop();
}
public String calculate(String first, String second, String operator){
boolean firstIsNumber = first.matches(ONLYNUMBERS);
boolean secondIsNumber = second.matches(ONLYNUMBERS);
if(firstIsNumber && secondIsNumber){
return calculateNumber(first, second, operator);
} else if(firstIsNumber && !secondIsNumber){
StringBuilder builder = new StringBuilder();
String[] parts = second.split(" ");
boolean added = false;
for(int i = 0; i < parts.length; i++){
String part = parts[i];
if(operators.contains(part)) builder.append(part + " ");
else if(part.matches(ONLYNUMBERS)){
added = true;
builder.append(calculateNumber(first, part, operator) + " ");
} else if(operator.equals("*") || operator.equals("/")){
int j = part.length() - 1;
for(; j > 0; j--){
if(part.substring(0,j).matches(ONLYNUMBERS)){
builder.append(calculateNumber(first, part.substring(0,j), operator) + part.substring(j) + " ");
break;
}
}
if(j == 0) {
builder.append(calculateNumber("1", second, operator) + part + " ");
}
} else {
builder.append(part + " ");
}
}
if((operator.equals("+") || operator.equals("-")) && added == false){
builder.insert(0, first + " " + operator + " ");
}
return builder.toString();
} else if(!firstIsNumber && secondIsNumber){
String[] parts = first.split(" ");
StringBuilder builder = new StringBuilder();
boolean added = false;
for(int i = 0; i < parts.length; i++){
String part = parts[i];
if(operators.contains(part)) builder.append(part + " ");
else if(part.matches(ONLYNUMBERS)){
added = true;
builder.append(calculateNumber(part, second, operator) + " ");
} else if(operator.equals("*") || operator.equals("/")){
int j = part.length() - 1;
for(; j > 0; j--){
if(part.substring(0,j).matches(ONLYNUMBERS)){
builder.append(calculateNumber(part.substring(0,j), second, operator) + part.substring(j, part.length()) + " ");
break;
}
}
if(j == 0){
builder.append(calculateNumber("1", second, operator) + part + " ");
}
} else {
builder.append(part + " ");
}
}
if((operator.equals("+") || operator.equals("-")) && added == false){
builder.append(operator + " " + second + " ");
}
return builder.toString();
} else {
if(operator.equals("+") || operator.equals("-")){
StringBuilder builder = new StringBuilder();
String[] firstParts = first.split(" ");
String[] secondParts = second.split(" ");
for(int i = 0; i < firstParts.length; i++){
String firstPart = firstParts[i];
if(operator.contains(firstPart)) {
builder.append(firstPart + " ");
continue;
}
for(int j = 0; j < secondParts.length; j++){
String secondPart = secondParts[j];
if(firstPart.matches(ONLYNUMBERS) && secondPart.matches(ONLYNUMBERS)){
builder.append(calculateNumber(firstPart, secondPart, operator));
break;
} else if(!firstPart.matches(ONLYNUMBERS) && !secondPart.matches(ONLYNUMBERS)){
int p = firstPart.length() - 1;
for(; p > 0 && !firstPart.substring(0,p).matches(ONLYNUMBERS); p--);
int q = secondPart.length() - 1;
for(; q > 0 && !firstPart.substring(0,q).matches(ONLYNUMBERS); q--);
builder.append(calculateNumber(p == 0? "1" : firstPart.substring(0, p), q == 0? "1" : secondPart.substring(0, q), operator) + firstPart.substring(p));
break;
}
}
}
return builder.toString();
}
}
return "";
}
public String calculateNumber(String first, String second, String operator){
int num1 = Integer.parseInt(first);
int num2 = Integer.parseInt(second);
switch (operator){
case "+": return String.valueOf(num1 + num2);
case "-": return String.valueOf(num1 - num2);
case "*": return String.valueOf(num1 * num2);
case "/": return String.valueOf(num1 - num2);
default: return "";
}
}
//（ x ＋ 1 ）＊ 3 ＋ 2 *（ 2x + 5 ） -> x 1 + 3 * 2 2x 5 + * +
public String[] convertRPN(String[] expression){
Stack<String> stack = new Stack<String>();
StringBuilder builder = new StringBuilder();
for(int i = 0; i < expression.length; i++){
String variable = expression[i];
if(variable.equals("(")) {
stack.push(variable);
} else if(operators.contains(variable)){
while(!stack.isEmpty() && highPriority(variable, stack.peek())){ //calculate the high
builder.append(stack.pop() + " ");
}
stack.push(variable);
} else if(variable.equals(")")){
while(!stack.isEmpty() && !stack.peek().equals("(")){
builder.append(stack.pop() + " ");
}
stack.pop();
} else builder.append(variable + " ");
}
while(!stack.isEmpty()){
builder.append(stack.pop() + " ");
}
return builder.toString().split(" ");
}
public boolean highPriority(String op1, String op2){
if((op1.equals("+") || op1.equals("-")) && (op2.equals("*") || op2.equals("/"))) return true;
else return false;
}
public static void main(String[] args){
F5_SimplifyExpression simplifer = new F5_SimplifyExpression();
String expre = "( x + 1 ) * 3 + 2 * ( 2x + 5 )";
String[] expression = expre.split(" ");
String[] RPN = simplifer.convertRPN(expression);
//x 1 + 3 * 2 2x 5 + * +
for(int i = 0; i < RPN.length; i++){
System.out.print(RPN[i] + " ");
}
System.out.println();
String result = simplifer.simplify(RPN);
System.out.println(result);
}
}