doc: add info

Author: JCPedroza

src/leet-code/0001-two-sum/README.md

@@ -1,7 +1,8 @@
 # Two Sum
 
-Given an array of integers `nums` and an integer `target`, return the two
-indexes of the numbers that add up to `target`.
+Write a function `twoSum`, that takes an array of integers `nums` and an
+integer `target` as inputs, and returns the two indexes of the numbers that
+add up to `target`.
 
 * Assume that `nums` contains at most one solution.
 * Can't use the same element twice.

src/leet-code/0020-valid-parentheses/README.md

@@ -1,7 +1,12 @@
 # Valid Parentheses
 
-Given a string `str` consisting of the following characters: `'('`, `')'`,
-`'['`, `']'`, `'{'`, `'}'`, determine if `str` is valid.
+Write a function `hasValidParentheses`, that takes a string `str` as input, and
+determines whether `str` is valid.
+
+The input string `str` contains just the characters: `'('`, `')'`, `'['`, `']'`,
+`'{'`, `'}'`.
+
+Validation rules:
 
 * Open brackets must be closed by the same type of brackets.
 * Open brackets must be closed in the correct order.
@@ -46,3 +51,10 @@ time complexity.
 
 A better approach is to iterate through the string only once, using a stack
 to manage the state, achieving linear time complexity.
+
+## Complexity Analysis
+
+| solution | time   | space |
+| -------- | ------ | ----- |
+| replace  | O(n^2) | O(n)  |
+| stack    | O(n)   | O(n)  |