Finish Postfix Parse Tree

So Happy!!!
 postfix:

 expr->expr '+' s_term
     | expr '-' s_term
     | term

 s_term->s_term '*' factor
     | s_term '/' factor
     | factor

 factor-> num
     | '(' expr ')'

================
eg : parse "1+3*2"

output-->
[0 0] expr  [expr : [1 1] +|]
[1 1] +  [+ : [2 2] expr|[2 3] s_term|]
[2 2] expr  [expr : [3 4] 1|]
[3 4] 1
[2 3] s_term  [s_term : [3 5] *|]
[3 5] *  [* : [4 6] s_term|[4 7] factor|]
[4 6] s_term  [s_term : [5 8] 3|]
[5 8] 3
[4 7] factor  [factor : [5 9] 2|]
[5 9] 2
========
         expr
           |
           +
       /       \
     expr    s_term
       |            |
      1            *
                  /            \
                 s_term   factor
                  |             |
                  3           2