matematikk.net

Noen som kan en algoritme for å få et utrykk på postfix-form? Har vært borti jernbanealgoritmen for prefix, men har aldri en for postfix. Da jeg ville tro postfix er det idelle når man bygger en kalkulator

Dette er bare pseudokode, men det vil gi deg en idè om hvordan det kan gjøres.

convertToPostfix(infix)

operatorStack = new empty stack
postfix = new empty string

while (infix has characters left to parse) {
nextCharacter = next nonblank character of infix
switch (nextCharacter) {
case variable:
Append nextCharacter to postfix
break
case '^':
operatorStack.push(nextCharacter)
break
case '+': case '-': case '*': case '/':
while (!operatorStack.isEmpty() and precedence of nextCharacter
<= precedence of operatorStack.peek()) {
Append operatorStack.peek() to postfix
operatorStack.pop()
}
operatorStack.push(nextCharacter)
break
case '(':
operatorStack.push(nextCharacter)
break
case ')':
topOperator = operatorStack.pop()
while (topOperator != '(') {
Append topOperator to postfix
topOperator = operatorStack.pop()
}
break
default: break
} // end switch
} // end while

while (!operatorStack.isEmpty()) {
topOperator = operatorStack.pop()
Append topOperator to postfix
}
return postfix

takker, skal klare det nå