hyfrey

/*
Given n, generate all structurally unique BST's (binary search trees) that 
store values 1...n.

For example,
Given n = 3, your program should return all 5 unique BST's shown below.

   1         3     3      2      1
    \       /     /      / \      \
     3     2     1      1   3      2

hyfrey

class Solution {
public:
    bool dfs(const string &s1, int i, const string &s2, int j, const string&s3, int k, vector<vector<int> > &dp) {   
        if(i == s1.size() && j == s2.size() && k == s3.size()) {
            return true;
        } 
        
        if(i == s1.size()) {
            return s2.substr(j) == s3.substr(k);
        }

hyfrey

/*
Given a collection of intervals, merge all overlapping intervals.

For example,
Given [1,3],[2,6],[8,10],[15,18],
return [1,6],[8,10],[15,18].
*/

/**
 * Definition for an interval.

hyfrey

/*
Given a m x n grid filled with non-negative numbers, 
find a path from top left to bottom right which minimizes 
the sum of all numbers along its path.

Note: You can only move either down or right at any point in time.
*/

class Solution {
public:

hyfrey

/*
Symmetric Tree
Given a binary tree, check whether it is a mirror of itself 
(ie, symmetric around its center).

For example, this binary tree is symmetric:

    1
   / \
  2   2

hyfrey

/*
Given a 2D board and a word, find if the word exists in the grid.

The word can be constructed from letters of sequentially 
cell, where "adjacent" cells are those horizontally or vertically
neighboring. The same letter cell may not be used more than once.

For example,
Given board =

hyfrey

/*
Given a sorted array and a target value, return the index if the target is found.
 If not, return the index where it would be if it were inserted in order.

You may assume no duplicates in the array.

Here are few examples.
[1,3,5,6], 5 → 2
[1,3,5,6], 2 → 1
[1,3,5,6], 7 → 4

hyfrey

/*
The string "PAYPALISHIRING" is written in a zigzag pattern on a given number of rows like 
this: (you may want to display this pattern in a fixed font for better legibility)

P   A   H   N
A P L S I I G
Y   I   R
And then read line by line: "PAHNAPLSIIGYIR"
Write the code that will take a string and make this conversion given a number of rows:

hyfrey

/*
Unique Binary Search Trees
Given n, how many structurally unique BST's (binary search trees) that store values 1...n?

For example,
Given n = 3, there are a total of 5 unique BST's.

   1         3     3      2      1
    \       /     /      / \      \
     3     2     1      1   3      2

hyfrey

#include <iostream>

using namespace std;

/*
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1
*/