Update 227-basic-calculator-ii.js

Author: everthis

227-basic-calculator-ii.js

@@ -1,3 +1,36 @@
+/**
+ * @param {string} s
+ * @return {number}
+ */
+const calculate = function(s) {
+  const stk = []
+  let op = '+', num = 0
+  s = s.trim()
+  const isDigit = ch => ch >= '0' && ch <= '9'
+  for(let i = 0, n = s.length; i < n; i++) {
+    const ch = s[i]
+    if(ch === ' ') continue
+    if(isDigit(ch)) {
+      num = (+num) * 10 + (+ch)
+    } 
+    if(!isDigit(ch) || i === n - 1) {
+      if(op === '-') stk.push(-num)
+      else if(op === '+') stk.push(num)
+      else if(op === '*') stk.push(stk.pop() * num)
+      else if(op === '/') stk.push(~~(stk.pop() / num))
+      
+      op = ch
+      num = 0
+    }
+  }
+  let res = 0  
+  for(const e of stk) res += e
+
+  return res
+};
+
+// another
+
 /**
  * @param {string} s
  * @return {number}