1. import java.util.Scanner;
2. import java.util.Stack;
4. public class JAVA {
6. /**
7. * @param args
8. */
9. public static void main(String[] args) {
10. Scanner scan = new Scanner(System.in);
11. while (scan.hasNext()) {
12. String str = scan.nextLine();
13. String s[] = str.split(" ");
14. char c[] = new char[s.length];
15. /*
16. * String陣列 s[] 轉成char 陣列 c[] 使用char 而不用String 是因為 char
17. * 有isDigit方法可以判斷是否是數字 ，比較方便
18. */
19. for (int i = 0; i < s.length; i++) {
20. c[i] = s[i].charAt(0);
21. }
23. // System.out.print(ChangetoPostfix(c));
24. System.out.println(ChangeToInfix(ChangetoPostfix(c)));
25. }
26. }
28. static char[] ChangetoPostfix(char c[]) {
29. StringBuffer sb = new StringBuffer();
30. Stack<Character> stack = new Stack<Character>();
31. char op;
32. for (int i = 0; i < c.length; i++) {
33. op = c[i];
34. // 如果是運算子
35. if (Character.isDigit(op))
36. sb.append(op);
37. else if (op == '(') {
38. stack.push(op);
39. } else if (op == ')') { // 遇到 ) 時,若stack.peek()的不是 ( ,就一直pop()出來
40. while (stack.peek() != '(') { // stack.peek():傳回Top的值 ，而不移除他
41. sb.append(stack.pop());
42. }
43. stack.pop(); // 拿出 (
44. }
46. else {
47. while (true) {
48. if (stack.empty()) {
49. stack.push(op);
50. break;
51. } else {
52. if (getPriority(op) <= getPriority(stack.peek())) {
53. sb.append(stack.pop()); // 如果輸入的優先序小於stack.peek()就pop
54. } else {
55. stack.push(op);
56. break;
57. }
58. }
59. }
61. }
62. }
64. while (!stack.empty()) { // 將剩下在堆疊裡的element都拿出來
65. sb.append(stack.pop());
66. }
67. return sb.toString().toCharArray();
68. }
70. static int getPriority(char c) { // 取得運算子優先序
71. switch (c) {
72. case '+':
73. case '-':
74. return 1;
75. case '*':
76. case '/':
77. case '%':
78. return 2;
79. default: // 非運算子回傳0
80. return 0;
81. }
82. }
84. static int ChangeToInfix(char p[]) {
85. Stack<Integer> stack = new Stack<Integer>();
86. char token;
87. for (int i = 0; i < p.length; i++) {
88. token = p[i];
89. if (Character.isDigit(token)) {
90. stack.push(Integer.parseInt(String.valueOf(p[i])));
91. } else {
92. stack.push(getCal(stack.pop(), stack.pop(), token));
93. }
94. }
95. return stack.pop();
96. }
98. static int getCal(int i2, int i1, char token) {
99. switch (token) {
100. case '+':
101. return i1 + i2;
102. case '-':
103. return i1 - i2;
104. case '*':
105. return i1 * i2;
106. case '/':
107. return i1 / i2;
108. case '%':
109. return i2 % i1;
111. }
112. return 0;
113. }
114. }

自己測試答案都正確

但是怎麼會測出RE 呢

求解