new

Author: yubinbai

README.md

@@ -3,6 +3,7 @@ Leetcode solutions in Java and Python
 
 |#|Title|Solution|Difficulty|
 |---|-----|--------|----------|
+|227|[Basic Calculator II](https://leetcode.com/problems/basic-calculator-ii/)|[Java](./src/basic_calculator_ii)|Medium|
 |226|[Invert Binary Tree](https://leetcode.com/problems/invert-binary-tree/)|[Java](./src/invert_binary_tree)|Easy|
 |225|[Implement Stack using Queues](https://leetcode.com/problems/implement-stack-using-queues/)|[Java](./src/implement_stack_using_queues)|Medium|
 |224|[Basic Calculator](https://leetcode.com/problems/basic-calculator/)|[Java](./src/basic_calculator)|Medium|

src/basic_calculator_ii/README.md

@@ -0,0 +1,14 @@
+Problem
+===
+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.
+
+You may assume that the given expression is always valid.
+
+	Some examples:
+	"3+2*2" = 7
+	" 3/2 " = 1
+	" 3+5 / 2 " = 5
+	
+Note: Do not use the eval built-in library function.

src/basic_calculator_ii/Solution.java

@@ -0,0 +1,34 @@
+import java.util.*;
+
+public class Solution {
+
+	public int calculate(String s) {
+		StringTokenizer tokens = new StringTokenizer('+' + s.replace(" ", "") + "+0", "+-*/", true);
+		long total = 0, term = 0;
+		while (tokens.hasMoreTokens()) {
+			String op = tokens.nextToken();
+			if ("+-".contains(op)) {
+				total += term;
+				term = (op.equals("+") ? 1 : -1) * Long.parseLong(tokens.nextToken());
+			} else {
+				long n = Long.parseLong(tokens.nextToken());
+				if (op.equals("*")) {
+					term *= n;
+				} else {
+					term /= n;
+				}
+			}
+		}
+		return (int)total;
+	}
+
+	public static void main(String[] args) {
+		Solution s = new Solution();
+		System.out.println(s.calculate("3+2*2"));
+		System.out.println(s.calculate(" 2-1 + 2 "));
+		System.out.println(s.calculate(" 3+5 / 2 "));
+		System.out.println(s.calculate(" 0-2147483648"));
+		System.out.println(s.calculate("1/2/3"));
+		System.out.println(s.calculate("100000000/1/2/3/4/5/6/7/8/9/10"));
+	}
+}