Add solution #402

Author: JoshCrozier

README.md

@@ -320,6 +320,7 @@
 399|[Evaluate Division](./0399-evaluate-division.js)|Medium|
 400|[Nth Digit](./0400-nth-digit.js)|Medium|
 401|[Binary Watch](./0401-binary-watch.js)|Easy|
+402|[Remove K Digits](./0402-remove-k-digits.js)|Medium|
 404|[Sum of Left Leaves](./0404-sum-of-left-leaves.js)|Easy|
 405|[Convert a Number to Hexadecimal](./0405-convert-a-number-to-hexadecimal.js)|Easy|
 407|[Trapping Rain Water II](./0407-trapping-rain-water-ii.js)|Hard|

solutions/0402-remove-k-digits.js

@@ -0,0 +1,33 @@
+/**
+ * 402. Remove K Digits
+ * https://leetcode.com/problems/remove-k-digits/
+ * Difficulty: Medium
+ *
+ * Given string num representing a non-negative integer num, and an integer k, return
+ * the smallest possible integer after removing k digits from num.
+ */
+
+/**
+ * @param {string} num
+ * @param {number} k
+ * @return {string}
+ */
+var removeKdigits = function(num, k) {
+  const stack = [];
+
+  for (const n of num) {
+    while (k > 0 && stack.length && stack[stack.length - 1] > n) {
+      stack.pop();
+      k--;
+    }
+    stack.push(n);
+  }
+
+  while (k > 0) {
+    stack.pop();
+    k--;
+  }
+
+  const result = stack.join('').replace(/^0+/, '');
+  return result.length ? result : '0';
+};