/*
 * 創(chuàng)建日期 2006-9-9
 *
 * TODO 要更改此生成的文件的模板，請(qǐng)轉(zhuǎn)至
 * 窗口 － 首選項(xiàng) － Java － 代碼樣式 － 代碼模板
 */
package calculator;

/**
 * @author 
 *
 * TODO 要更改此生成的類型注釋的模板，請(qǐng)轉(zhuǎn)至
 * 窗口 － 首選項(xiàng) － Java － 代碼樣式 － 代碼模板
 */
public class Calculate {

	private String infix;	// 四則運(yùn)算表達(dá)式(中綴)
	
	// 構(gòu)造函數(shù)
	public Calculate(String s){
		infix = s;
	}
	
	//判斷有誤的輸入
	int Match(String exprString){
		
		int leng = exprString.length();		//所判斷字符串長(zhǎng)度
		char[] exp = new char[leng];		//數(shù)組exp用來存儲(chǔ)exprString各字符
		
		for(int i = 0; i < leng; i++){
			exp[i] = exprString.charAt(i);
		}
		
		char[] st = new char[leng];		//定義棧st來存放小括號(hào)
		int top = -1, i = 0, tag = 1;		//定義棧頂top和標(biāo)簽tag
		
		// 判斷式子中是否含有操作符
		for(int k = 0; k < leng; k ++){
			if(exp[k] == '*'||exp[k] == '/'||exp[k] == '+'||exp[k] == '-')
				break;
			else if(k == leng - 1)
				tag = 6;
		}
		
		while(i < leng && tag ==1){	
			
			// 判斷首字符是否非法(操作數(shù)未考慮到正負(fù))
			if(exp[0] == '*'||exp[0] == '/'||exp[0] == '.'||exp[0] == '+'||exp[0] == '-'){
				tag = 3;		//***首字符非法
				break;
			}
			
			// 判斷末尾字符是否非法
			if(exp[leng - 1] == '*'||exp[leng - 1] == '/'||exp[leng - 1] == '.'
				||exp[leng - 1] == '+'||exp[leng - 1] == '-'){
				tag = 5;		//***末尾字符非法
				break;
			}
			
			// 判斷 + - * / .是否有連續(xù)情況
			if(exp[i] == '*'||exp[i] == '/'||exp[i] == '.'||exp[i] == '+'||exp[i] == '-'){
				if(i > 0){
					i --;
					if(exp[i] == '*'||exp[i] == '/'||exp[i] == '.'||exp[i] == '+'||exp[i] == '-'){
						tag = 4;//***連續(xù)
						break;
					}else{
						i ++;
					}
				}
			}
			
			// 遇到非法字符
			if(!(exp[i] == '1'|| exp[i] == '2'|| exp[i] == '3'|| exp[i] == '4'|| exp[i] == '5'|| exp[i] == '6' 
				|| exp[i] == '7'|| exp[i] == '8'|| exp[i] == '9'|| exp[i] == '0'|| exp[i] == '+'|| exp[i] == '-'
					|| exp[i] == '*'|| exp[i] == '/'|| exp[i] == '('|| exp[i] == ')'|| exp[i] == '.'|| exp[i] == ' ')){
				tag = 2;			//***非法字符
				break;
			}
			
			if(exp[i] == '('){	// 遇到'(',將其入棧
				top ++;
				st[top] = exp[i];
			}
			
			if(exp[i] == ')'){	// 遇到')',若棧頂是'(',則繼續(xù)處理,否則以不配對(duì)返回
				if((top >= 0) && (st[top] == '(')) top --;
				else{
					tag = 0;	//***小括號(hào)不對(duì)稱
					break;
				}
			}
			
			i ++;
			
		}
		
		if(top >= 0) 			// 若棧不為空,則不配對(duì)
			tag = 0;
		
		return (tag);			//正常情況,tag為1
		
	}
	
	public String getResult(){
		
		String resuStr = "";	// 表示結(jié)果的字符串,為正確結(jié)果或者是其他信息
		String postfix = "";	// 后綴
		char[] operators = new char[infix.length()];	// 定義用于存放操作符的棧
		int top = -1;			// 棧頂
		int matc = Match(infix);
		
		if(matc == 3){
			resuStr = "首個(gè)字符有誤.";
		}else if(matc == 4){
			resuStr = "出現(xiàn)了連續(xù)的+-/*.!";
		}else if(matc == 2){
			resuStr = "您輸入了非法字符!";
		}else if(matc == 0){
			resuStr = "括號(hào)不配對(duì).";
		}else if(matc == 5){
			resuStr = "末尾字符出錯(cuò).";
		}else if(matc == 6){
			resuStr = "式子中缺少操作符.";
		}else{
			
			// 遍歷中綴
			for(int i = 0; i < infix.length(); i ++){
				
				char oper = infix.charAt(i);
				
				switch(oper)
				{
				case ' ':// 忽略空格
					break;
					
				case '+':// 操作符
				case '-':
					while(top >= 0){	// 棧不為空時(shí)
						char c = operators[top--];	// 出棧
						if(c == '('){
							operators[++top] = c;	// 遇到'(',將其重新入棧
							break;
						}else{
							postfix = postfix + c;	// 添加 c操作符到后綴中參與運(yùn)算
						}
					}
					operators[++top] = oper;		// 當(dāng)前操作符入棧
					postfix += " ";
				    break;
				    
				case '*':
				case '/':
					while(top >= 0){
						char c = operators[top--];
						if(c == '('){
							operators[++top] = c;
							break;
						}else{
							if(c == '+' || c == '-'){// 遇到加減號(hào),先進(jìn)行乘除運(yùn)算,故先將加減號(hào)壓入棧
								operators[++top] = c;
								break;
							}else{
								postfix = postfix + c;
							}
						}
					}
					operators[++top] = oper;
					postfix += " ";
				    break;
				    
				case '(':
					operators[++top] = oper;
					postfix += " ";
				    break;

				    
				case ')':
					while(top >= 0){
						char c = operators[top--];
						if(c == '('){	// 由于遇到')','('此后不再有效,故不需重新入棧
							break;
						}else{
							postfix = postfix + c;
						}
					}
					postfix += " ";
					break;
				    
				default:
					postfix = postfix + oper;
					break;
				}
			}
			
			while(top >= 0){
				postfix = postfix + operators[top--];
			}// 得到的是一條無括號(hào)的后綴表達(dá)式
			
			// 計(jì)算后綴表達(dá)式
			double[] operands = new double[postfix.length()];// 定義用來存放操作數(shù)的棧
			double x, y, z;
			top = -1;
			String operand = "";	// 定義操作數(shù)
			for(int j = 0; j < postfix.length(); j ++){
				
				char c = postfix.charAt(j);
				
				if((c >= '0' && c <= '9') || c == '.'){
					operand += c;
				}
				
				if(c == ' ' && operand != ""){
					operands[++top] = Double.parseDouble(operand);	// 完整操作數(shù)入棧
				    operand = "";
				}
				
				if(c == '+' || c == '-' || c == '*' || c == '/'){
					if(operand != ""){
						operands[++top] = Double.parseDouble(operand) ;
					    operand = "";
					}
					y = operands[top--]; // 彈出雙目運(yùn)算符的第二操作數(shù)
					x = operands[top--]; // 彈出雙目運(yùn)算符的第一操作數(shù)
					switch(c)
					{
					case '+' :
						z = x + y;
					    break;
					case '-' :
					    z = x - y;
					    break;
					case '*' :
					    z = x * y;
					    break;
					case '/' :
					    z = x / y;
					    break;
					default :
						z = 0;
					    break;
					}
					operands[++top] = z; // 中間結(jié)果再次入棧,其位置為上述x的位置
				}
				
			}
			z = operands[top--]; 		// 彈出最終結(jié)果
			resuStr = Double.toString(z);
		}
		return resuStr;
	}
}