Add solution #227

Author: JoshCrozier

0227-basic-calculator-ii.js

@@ -0,0 +1,37 @@
+/**
+ * 227. Basic Calculator II
+ * https://leetcode.com/problems/basic-calculator-ii/
+ * Difficulty: Medium
+ *
+ * Given a string s which represents an expression, evaluate this expression and return its value.
+ *
+ * The integer division should truncate toward zero.
+ *
+ * You may assume that the given expression is always valid. All intermediate results will be in
+ * the range of [-231, 231 - 1].
+ *
+ * Note: You are not allowed to use any built-in function which evaluates strings as mathematical
+ * expressions, such as eval().
+ */
+
+/**
+ * @param {string} s
+ * @return {number}
+ */
+var calculate = function(s) {
+  const stack = [];
+
+  for (let i = 0, num = 0, sign = '+'; i < s.length; i++) {
+    if (s[i] >= '0' && s[i] <= '9') num = num * 10 + (s[i] - '0');
+    if ((s[i] < '0' && s[i] !== ' ') || i === s.length - 1) {
+      if (sign === '+') stack.push(num);
+      else if (sign === '-') stack.push(-num);
+      else if (sign === '*') stack.push(stack.pop() * num);
+      else if (sign === '/') stack.push(Math.trunc(stack.pop() / num));
+      sign = s[i];
+      num = 0;
+    }
+  }
+
+  return stack.reduce((a, b) => a + b, 0);
+};

README.md

@@ -208,6 +208,7 @@
 224|[Basic Calculator](./0224-basic-calculator.js)|Hard|
 225|[Implement Stack using Queues](./0225-implement-stack-using-queues.js)|Easy|
 226|[Invert Binary Tree](./0226-invert-binary-tree.js)|Easy|
+227|[Basic Calculator II](./0227-basic-calculator-ii.js)|Medium|
 228|[Summary Ranges](./0228-summary-ranges.js)|Easy|
 229|[Majority Element II](./0229-majority-element-ii.js)|Medium|
 230|[Kth Smallest Element in a BST](./0230-kth-smallest-element-in-a-bst.js)|Medium|