Update README - Topic Tags

Author: MukulParasar

README.md

@@ -37,10 +37,27 @@ https://leetcode.com/u/mukul_parashar/
 |  |
 | ------- |
 | [0033-search-in-rotated-sorted-array](https://github.com/MukulParasar/leetcode-java-solutions/tree/master/0033-search-in-rotated-sorted-array) |
+| [0042-trapping-rain-water](https://github.com/MukulParasar/leetcode-java-solutions/tree/master/0042-trapping-rain-water) |
 | [0081-search-in-rotated-sorted-array-ii](https://github.com/MukulParasar/leetcode-java-solutions/tree/master/0081-search-in-rotated-sorted-array-ii) |
 ## Binary Search
 |  |
 | ------- |
 | [0033-search-in-rotated-sorted-array](https://github.com/MukulParasar/leetcode-java-solutions/tree/master/0033-search-in-rotated-sorted-array) |
 | [0081-search-in-rotated-sorted-array-ii](https://github.com/MukulParasar/leetcode-java-solutions/tree/master/0081-search-in-rotated-sorted-array-ii) |
+## Two Pointers
+|  |
+| ------- |
+| [0042-trapping-rain-water](https://github.com/MukulParasar/leetcode-java-solutions/tree/master/0042-trapping-rain-water) |
+## Dynamic Programming
+|  |
+| ------- |
+| [0042-trapping-rain-water](https://github.com/MukulParasar/leetcode-java-solutions/tree/master/0042-trapping-rain-water) |
+## Stack
+|  |
+| ------- |
+| [0042-trapping-rain-water](https://github.com/MukulParasar/leetcode-java-solutions/tree/master/0042-trapping-rain-water) |
+## Monotonic Stack
+|  |
+| ------- |
+| [0042-trapping-rain-water](https://github.com/MukulParasar/leetcode-java-solutions/tree/master/0042-trapping-rain-water) |
 <!---LeetCode Topics End-->