Leetcode--basic Calculator II

Description:

Implement a basic calculator to evaluate a simple expression string.

The expression string contains only non-negative integers,,, + - * , / operators and empty spaces . The integer division should truncate toward zero.

Assume that the given expression was always valid.

Some Examples:

"3+2*2" = 7 "3/2" = 1 "3+5/2" = 5

Note: don't use the eval built-in library function.

Handles data and operators with two stack of operations. Calculate * and/Then add and subtract and then calculate sequentially.

public class Solution {public static int calculate (String s) {stack<integer> num = new stack<> ();        Stack<character> op = new stack<> ();        Op.push (' + ');        int n = s.length ();        if (n < 1) return 0; for (int i=0; i<n;)        {if (S.charat (i) = = ") {i + +;        } else if (IsOp (S.charat (i))) {Op.push (S.charat (i));        i + +;        } else {int temp = 0;        while (I < n && isdigit (S.charat (i))) {temp = temp * 10;        Temp + = S.charat (i)-' 0 ';        i + +; } if (!op.empty () && (op.peek () = = ' * ' | | op.peek () = = '/')) {if (Op.peek () = = ' * ') {temp *= num.        Pop ();        Op.pop ();        } else {temp = Num.pop ()/temp;        Op.pop ();        }} num.push (temp);        }} int res = 0;          while (!op.empty ()) {int temp = Num.peek ();      SYSTEM.OUT.PRINTLN (temp);  if (op.peek () = = '-') temp =-temp;          res + = temp;          Num.pop ();          Op.pop ();            } return res; }public Static Boolean isOp (char c) {if (c = = ' + ' | | c = = '-' | | c = = ' * ' | | c = = '/') {return true;} else {return false;}} public static Boolean isdigit (char c) {if (c >= ' 0 ' && C <= ' 9 ') {return true;} else {return false;}}}

Leetcode--basic Calculator II