/**
 * Created With IntelliJ IDEA.
 * Descriptions:
 * 1、定義一個棧stack，用來接收運算子；定義一個char型別陣列chars，用於接收輸出結果
 * 2、從左到右遍歷字串，遇到字元新增到輸chars，遇到運算子棧為空入棧，不為空，
 * 當前運算子A和棧頂運算子B比較，如果A的優先順序大於B，那麼A入棧，否則A出棧，並新增到chars，B入棧
 * 3、遇到左括號入棧，右括號則進行出棧操作，直到匹配到左括號，出棧結束
 * 4、將棧中剩餘元素加入到chars中
 * User:Mr.Du
 * Date:2021/6/19
 * Time:21:22
 
 
*/

/**
     *
     * @param s        輸入表示式
     * @param stack   儲存操作符和括號
     * @return
     */
    public static String infixToPostFix(String s, Stack<Character> stack){
        int index = 0;
        char[] tmp = s.toCharArray();
        char[] chars = new char[s.length()];
        for(int i = 0;i < s.length();i++){
 
//            (a+b)*c+d*(e+f)
            if(tmp[i] >= '0' && tmp[i] <= '9'){
                chars[index++] = tmp[i];
            }else if(tmp[i] == '('){
                stack.add(tmp[i]);
            }else if(tmp[i] == '+' || tmp[i] == '-'
                        || tmp[i] == '*'
                        || tmp[i] == '/'){
                
 
if(!stack.isEmpty()){
                    char c = stack.peek();
                    if(c == '('){
                        stack.push(tmp[i]);
                    } else if(getPriority(tmp[i],c)){
                        stack.push(tmp[i]);
                    }else{
                        chars[index++] = c;
                        stack.pop();
                        stack.push(tmp[i]);
                    }
                }else{
                    stack.push(tmp[i]);
                }

            }else if(tmp[i] == ')'){
                char c;
                while((c = stack.pop()) != '('){
                    chars[index++] = c;
                }

            }
        }
        while(!stack.isEmpty()){
            chars[index++] = stack.pop();
        }
        return String.valueOf(chars);
    }

    /**
     * 比較算術運算子大小
     * @param a
     * @param b
     * @return   true代表a的優先順序高於b
     */
    public static boolean getPriority(char a,char b){
        if((a == '*' || a == '/') && (b == '+' || b == '-')) return true;
        return false;
    }