ZH cheese: Python infix expression conversion suffix expression

A program that implements an infix expression conversion suffix expression that can handle the addition and subtraction of multiplier operations:

An input infix expression inorder

A pool of output pools

A stack of cache stacks

Read Inorder verbatim from front to back

First look at the brackets that do not include:

(1) Operand: direct output to Pool

(2) Operator: Determines the precedence of the current operator and the Stack[top] operator

<1> current operator precedence higher than stack[top]: Adds the current operator to the stack;

<2> the current operator priority is less than or equal to Stack[top]: start the stack from stack[top], until Stack[top] takes precedence over the current operator and then the current operator into the stack;

(3) When the Inorder traversal is complete, if the stack is not empty, reverse the stack and add to the pool tail

1 __author__='Zhanghe'2 defIn2post (inorder):3Pool ="'4stack ="'5      forIinchinorder:6RET =proc (I,switch (i), Stack,pool)7stack = ret['Stack']8Pool = ret['Pool']9     ifStack! ="':Tenstack = stack[::-1] One     returnpool+Stack A  - defswitch (c): -Operator1 ='+-' theOperator2 ='*/' -num ='ABCDEFG' -     ifCinchNum: -         return0 +     ifCinchOperator1: -         return1 +     ifCinchOperator2: A         return2 at defproc (c,op,stack,pool): -top = len (stack)-1 -  -     ifOp = = 0:#ABCDEFG -Pool + =C -     ifOP = = 2orOp==1:#* in         iftop = =-1: -Stack + =C to         elifSwitch (Stack[top]) <op: +Stack + =C -         Else: the              whileTop! =-1 andSwitch (Stack[top]) >=op: *Pool + =Stack[top] $Top-= 1Panax Notoginseng             ifTop! =-1: -stack = stack[0:top+1] the             Else: +stack ="' AStack + =C theRET = { +         'Stack': Stack, -         'Pool':p ool $     } $     returnret -Inorder ='a+b*c-d*e+f/g'print In2post (inorder)

What factors should be considered when enclosing parentheses?

On the basis of the previous procedure, consider the following points further:

(4) After the parentheses, "(" has the highest priority, that is, encountered "(" Put in the stack is OK;

(5) ")" operation is also relatively simple, directly to the stack of elements popped into the pool, until the popup "(";

A new operator rule is required:

(5) Operator: Determines the precedence of the current operator and the Stack[top] operator

<1> the current operator precedence is higher than stack[top] or stack[top]== ' (': adds the current operator to the stack;

<2> the current operator priority is less than or equal to Stack[top]: from Stack[top] start out of the stack until Stack[top] priority is higher than the current operator or Stack[top] is "(", then the current operator into the stack;

1 __author__='Zhanghe'2 defIn2post (inorder):3Pool ="'4stack ="'5      forIinchinorder:6RET =proc (I,switch (i), Stack,pool)7stack = ret['Stack']8Pool = ret['Pool']9     ifStack! ="':Tenstack = stack[::-1] One     returnpool+Stack A  - defswitch (c): -Operator1 ='+-' theOperator2 ='*/' -Operator3 =')' -Operator4 ='(' -num ='ABCDEFG' +     ifCinchNum: -         return0 +     ifCinchOperator1: A         return1 at     ifCinchOperator2: -         return2 -     ifCinchOperator3: -         return3 -     ifCinchOperator4: -         return4 in defproc (c,op,stack,pool): -top = len (stack)-1 to  +     ifOp = = 0:#ABCDEFG -Pool + =C the     ifOP = = 2orOp==1:#* *         iftop = =-1: $Stack + =CPanax Notoginseng         elifSwitch (Stack[top]) < oporStack[top] = ='(': -Stack + =C the         Else: +              whileTop! =-1 andSwitch (Stack[top]) >= op andSwitch (Stack[top]) <switch (')'): APool + =Stack[top] theTop-= 1 +             ifTop! =-1: -stack = stack[0:top+1] $             Else: $stack ="' -Stack + =C -     ifOP = = 3:#) the          whiletop!=-1 andStack[top]! ='(': -Pool + =Stack[top]WuyiTop-= 1 thestack =Stack[0:top] -     ifOP = = 4:#( WuStack + =C -RET = { About         'Stack': Stack, $         'Pool':p ool -     } -     returnret - #inorder = ' a+b*c-d*e+f/g ' AInorder ='a+b*c+ (d*e+f) *g' + PrintIn2post (inorder)

Output:

abc*+de*f+g*+

ZH cheese: Python infix expression conversion suffix expression