Create evaluate-reverse-polish-notation.js

Author: zeyadetman

leetcode/evaluate-reverse-polish-notation.js

@@ -0,0 +1,29 @@
+var evalRPN = function(tokens) {
+ const stack = []; // ["2", "1", "+", "3", "*"]
+ let i = 0;
+ if(tokens.length === 1) return Number(tokens[0]);
+ stack.push(tokens[i++]);
+ stack.push(tokens[i++]);
+ while(stack.length && tokens[i]) {
+ if(!isNaN(tokens[i])) {
+ stack.push(tokens[i]);
+ } else {
+ const num2 = Number(stack.pop());
+ const num1 = Number(stack.pop());
+ if(tokens[i] === '+') stack.push(num1 + num2);
+ if(tokens[i] === '*') stack.push(num1 * num2);
+ if(tokens[i] === '-') stack.push(num1 - num2);
+ if(tokens[i] === '/') stack.push(
+ Math.trunc(num1 / num2)
+ );
+ }
+ i++;
+ };
+
+ return stack.pop();
+};
+
+//test cases
+[["2", "1", "+", "3", "*"], ["18"], ["4", "13", "5", "/", "+"], ["10", "6", "9", "3", "+", "-11", "*", "/", "*", "17", "+", "5", "+"]].map(v => {
+ console.log(evalRPN(v));
+});