nyist oj 467 （中缀式变后缀式）

题目链接：http://acm.nyist.net/JudgeOnline/problem.php?pid=467
直接上代码：
  1 #include <cstdio>
  2 #include <cstring>
  3 using namespace std;
  4 
  5 const int N = 1001;
  6 char stack[N];
  7 char op[N];
  8 char s[N];
  9 int top;
 10 int top_op;
 11 
 12 int compare(char a);
 13 void translate();
 14 
 15 int main()
 16 {
 17      int t;
 18      scanf("%d", &t);
 19      while(t--)
 20      {
 21           translate();           
 22     }
 23      return 0;     
 24 }
 25 
 26 int compare(char a)
 27 {
 28      switch(a)
 29     {
 30               case '+':
 31              case '-':
 32                    return 1;
 33              case '*':
 34              case '/':
 35                    return 2;
 36              case '(':
 37                    return 0;
 38              default:
 39                    return -1;          
 40     }     
 41 }
 42 
 43 void translate()
 44 {
 45       scanf("%s", s);
 46       int len = strlen(s) - 1;
 47       top = -1;
 48       top_op = -1;
 49       for(int i = 0; i < len; i++)
 50       {
 51                  if('0' <= s[i] && s[i] <= '9' || s[i] == '.')
 52               {
 53                      top++;
 54                      stack[top] = s[i];          
 55               }           
 56               else if(s[i] == '(')
 57               {
 58                      top_op++;
 59                      op[top_op] = s[i];           
 60               }
 61               else if(s[i] == ')')
 62               {
 63                      while(op[top_op] != '(')
 64                      {
 65                              top++;
 66                              stack[top] = ' ';
 67                              top++;
 68                              stack[top] = op[top_op];
 69                              top_op--;                 
 70                      }   
 71                      top_op--;  
 72               }
 73               else if(s[i] == '+' || s[i] == '-' || s[i] == '*' || s[i] == '/')
 74               {
 75                      top++;
 76                      stack[top] = ' ';
 77                      if(top_op != -1)
 78                      {
 79                             while(compare(s[i]) <= compare(op[top_op]))
 80                             {
 81                                    top++;
 82                                    stack[top] = op[top_op];
 83                                    top++;
 84                                    stack[top] = ' ';                            
 85                                    top_op--;                        
 86                            }  
 87                      }
 88                      top_op++;
 89                      op[top_op] = s[i];  
 90               }
 91       }            
 92       while(top_op != -1)
 93       {
 94               top++;
 95               stack[top] = ' ';
 96               top++;
 97               stack[top] = op[top_op];
 98               top_op--;             
 99       }
100       top++;
101       stack[top] = ' ';
102       top++;
103       stack[top] = '=';
104       top++;
105       stack[top] = '\0';
106       printf("%s\n", stack);
107 }