Add solution #636

Author: JoshCrozier

Diff for: README.md

@@ -478,6 +478,7 @@
 629|[K Inverse Pairs Array](./0629-k-inverse-pairs-array.js)|Hard|
 630|[Course Schedule III](./0630-course-schedule-iii.js)|Hard|
 633|[Sum of Square Numbers](./0633-sum-of-square-numbers.js)|Medium|
+636|[Exclusive Time of Functions](./0636-exclusive-time-of-functions.js)|Medium|
 637|[Average of Levels in Binary Tree](./0637-average-of-levels-in-binary-tree.js)|Easy|
 643|[Maximum Average Subarray I](./0643-maximum-average-subarray-i.js)|Easy|
 645|[Set Mismatch](./0645-set-mismatch.js)|Medium|

Diff for: solutions/0636-exclusive-time-of-functions.js

@@ -0,0 +1,56 @@
+/**
+ * 636. Exclusive Time of Functions
+ * https://leetcode.com/problems/exclusive-time-of-functions/
+ * Difficulty: Medium
+ *
+ * On a single-threaded CPU, we execute a program containing n functions. Each function has a
+ * unique ID between 0 and n-1.
+ *
+ * Function calls are stored in a call stack: when a function call starts, its ID is pushed
+ * onto the stack, and when a function call ends, its ID is popped off the stack. The function
+ * whose ID is at the top of the stack is the current function being executed. Each time a
+ * function starts or ends, we write a log with the ID, whether it started or ended, and the
+ * timestamp.
+ *
+ * You are given a list logs, where logs[i] represents the ith log message formatted as a string
+ * "{function_id}:{"start" | "end"}:{timestamp}". For example, "0:start:3" means a function call
+ * with function ID 0 started at the beginning of timestamp 3, and "1:end:2" means a function
+ * call with function ID 1 ended at the end of timestamp 2. Note that a function can be called
+ * multiple times, possibly recursively.
+ *
+ * A function's exclusive time is the sum of execution times for all function calls in the program.
+ * For example, if a function is called twice, one call executing for 2 time units and another
+ * call executing for 1 time unit, the exclusive time is 2 + 1 = 3.
+ *
+ * Return the exclusive time of each function in an array, where the value at the ith index
+ * represents the exclusive time for the function with ID i.
+ */
+
+/**
+ * @param {number} n
+ * @param {string[]} logs
+ * @return {number[]}
+ */
+var exclusiveTime = function(n, logs) {
+  const stack = [];
+  const result = new Array(n).fill(0);
+  let previousTime = 0;
+
+  for (const log of logs) {
+    const [id, action, time] = log.split(':');
+    const currentTime = +time;
+
+    if (action === 'start') {
+      if (stack.length) {
+        result[stack[stack.length - 1]] += currentTime - previousTime;
+      }
+      stack.push(+id);
+      previousTime = currentTime;
+    } else {
+      result[stack.pop()] += currentTime - previousTime + 1;
+      previousTime = currentTime + 1;
+    }
+  }
+
+  return result;
+};