Implementation of the calculator data structure (JAVA) (iv)

principle:

1. Change the middle order expression to follow-up expression

2. The current character is a number, put that number in the stack

3. The current character is the operator, take out two trees from the stack, according to operator operation, put the result of the operation into the stack

4. Repeat until the character is finished, and there is only one element left in the stack, that is, the result of the operation

PS: I do not handle, can only run 10 of the operation, if necessary can be extended

Package Com.lip.datastructure.tree;import Java.util.iterator;import Java.util.stack;public class Calculator{public static void Main (string[] args) {String obj = "A * (b+c) +c/d"; String obj1 = "1+3 +9/3"; System.out.println (obj1+ "=" +calculator (obj1));} Use post-order expressions to calculate the///principle: 1. When the period character is a letter or a number, it is directly into the stack//2. The current character is an operator that takes out two numbers from the stack//3. Put the results of the calculation into the stack, the last remaining element of the stack is the result public static T Calculator (String obj) {string postobj=tranform (obj); System.out.println (); Stack<integer>stack=new stack<integer> (); for (int i=0;i<postobj.length (); i++) {char ch= Postobj.charat (i); if (Character.isletterordigit (CH))//character or number {Stack.push (Integer.parseint (ch+ ""));} else//operator {//Remove two number int op1,op2;op1=stack.pop (); Op2=stack.pop (); switch (CH) {case ' + ': Stack.push (OP2+OP1); Break;case ' -': Stack.push (OP2-OP1); Break;case ' * ': Stack.push (OP2*OP1); Break;case '/': Stack.push (OP2/OP1); break;default:break ;}}} return Stack.pop ();} The middle sequence traversal changes to subsequent traversal of public static string Tranform (String obj) {stack<character> Stack = new Stack<characteR> (); String obj2 = ""; for (int i = 0; I < obj.length (); i++) {Char ch = obj.charat (i), if (Character.isletterordigit (CH))//letter or digital Direct output {obj2 + = ch; System.out.print (CH);} else if (ch = = ') ') operations characters stop out of stack {char temp;while (temp = Stack.pop ())! = ' (') {obj2 + = temp; System.out.print (temp);}} else//the stack priority of the comparison operator {if (Stack.isempty ()) {Stack.push (ch); continue;} Char temp = Stack.peek (), while (ICP (CH) <= ISP (temp))//stack priority is less than the priority in the stack, the stack {System.out.print (temp); Obj2 + = temp; Stack.pop (); if (Stack.isempty ()) break;temp = Stack.peek ();} Stack.push (ch);}} Bounce the remaining elements out of the stack while (!stack.isempty ()) {Char temp = Stack.pop (); Obj2 + = temp; System.out.print (temp);} return obj2;} Operator precedence within stack private static int ISP (char ch) {switch (ch) {case ' + ': Case '-': return 2;case ' * ': Case '/': Return 4;case ') ': RE Turn 7;case ' (': Return 1;default:break;} return 0;} Precedence priority of the operator into the stack private static int ICP (char ch) {switch (ch) {case ' + ': Case '-': return 3;case ' * ': Case '/': Return 5;case ') ': Return 1;case ' (': return 7;default:break;}return 0;}} 

Implementation of the calculator data structure (JAVA) (iv)