docs: add README files for leetcode problems and table of contents

README.md

@@ -0,0 +1,26 @@
+# LeetCode
+
+<!--toc:start-->
+- [LeetCode](#leetcode)
+  - [Introduction](#introduction)
+  - [Frequency Map + Sort-With-Tiebreaker](#frequency-map-sort-with-tiebreaker)
+  - [Event Emitter + Throttle](#event-emitter-throttle)
+<!--toc:end-->
+
+## Introduction
+
+Day 1: Frequency map + sort-with-tiebreak until automatic (LC 1365, 1636, 451)
+Day 2: Write Event Emitter and Throttle from blank file, twice each (LC 2694, 2676, 359)
+Day 3: Pattern-deduction reps — grab LC easy problems, look only at examples, guess the rule, then verify. 10–15 reps
+
+## Frequency Map + Sort-With-Tiebreaker
+
+- [LC-1365](./lc-1365/README.md)
+- [LC-1636](./lc-1636/README.md)
+- [LC-451](./lc-451/README.md)
+
+## Event Emitter + Throttle
+
+- [LC-2694](./lc-2694/README.md)
+- [LC-2676](./lc-2676/README.md)
+- [LC-359](./lc-359/README.md)