I'm Richard Hayes

A Computer Science student at the University of Ottawa. I was a Microsoft Software Intern summer 2019. I recently built and published a Unity game called the central processing unit. Right now, I'm building a ReactJS app to allow students to interactively design a graph, write custom code in an in-browser editor, and animate the graph while steping over the code.

I'm also designing a tokenizer, lexer, and generator for a custom programing language called twenty-six which compiles to JS. Each week, I solve leet code challenges with friends for fun; I like learning about data structures, algorithims, and solving programing puzzles.

Projects

Recent Solutions

Trapping Rain Water

array two pointers stack
28 Jul 2019
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By moving once from left to right across the array of heights, it’s possible to calculate the total trapped rain water using a stack.

Daily Capacity

binary search optimization
1 Jun 2019
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To determine the minimum capacity required to ship all packages within D days, it was optimal to use a binary search. Assuming that the minimum weight was K, we know that all capacities less than K will fail and all capacities larger will succeed. Thus, we perform a binary search over the space of all possible capacities until we find then minimum capacity K such that k-1 is false.

Alien Rhyme

Suffix Tree Post Order strings
13 Apr 2019
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This problem is from Round 1A Google Code Jam 2019, I solved it by constructing a suffix tree, which I then traversed using a post order traversal in order to match strings into groups of two from longest to shortest suffix.

Puzzles

Shortest Path Sum

Floyd-Warshall graph algorithm

Given the hex string in the white box below. Construct a graph according to the following rules:

  • Each unique letter is a node.
  • Two nodes have an edge between them if they are adjacent in the string.
  • The weight of the edge between two nodes is the hex value of the two connected nodes.
  • If the same edge appears twice, ignore its second appearance.
  • The weight of an edge from a node to itself is zero.

Find the sum of every unique shortest path. Two shortest paths are unique if one of the paths contains at least one node that the other does not. The shortest path between two nodes is a series of edges along which one could travel to get from one node to the other.

Example The hex string 5d0d has 3 unique nodes 5, d, and 0. As we traverse the string from left to right, we find the following edges:

  • Edge 5d with value 5 + d = 5 + 13 = 18
  • Edge d0 with value d + 0 = 13 + 0 = 13
  • Edge 0d which is the same as d0, so we ignore it

We have 3 shortest paths to consider as follows:

  • Path 0 to d with a cost of 13
  • Path 0 to 5 with a cost of 31
  • Path d to 5 with a cost of 18
  • Note, the remaining paths would just be one of the above in reverse.

So, the answer to this example case is 13 + 31 + 18 = 62

61bffea9215f65164ad18b45aff1436c0c165d0d5dd2087ef61b4232ba6d2c1a

SUBMIT
CORRECT

Binary Search

binary search algorithm

Given the function below, find the largest integer n such that query(n) returns false and query(n+1) returns true. The answer is an integer between 1 and 80000000000 (80 billion!)

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function query(n) {
    let d1 = dist(n);
    let d2 = dist(n + 1);
    return d2 > d1;
}
function dist(v) {
    let c = (v + 28000000000)/10000000000;
    let t = c * Math.log(c)/2;
    let a = Math.pow(t - c, 2);
    let b1 = t + c;
    let b2 = c * Math.log(c);
    let b = Math.pow(b1 - b2, 2);
    return Math.sqrt(a + b);
}

SUBMIT
CORRECT

Odd and Even Numbers 😏

tricky logic

Find the missing value (hint: read the title):

  • 80618 = 4
  • 10792 = 2
  • 21643 = 3
  • 75335 = 0
  • 44713 = ?

SUBMIT
CORRECT

Videos

I make youtube videos about Unity, Git, Servers, and Algorithims.

Games

Maze

JOIN

Use arrow keys to move. Collect the gold before the other players. This is multiplayer game with anyone else on this site. Written with NodeJS and Socket.io. Player list and scores are shown below:

Spread

START

Spread is a game about strategically selecting a starting point for a virus. Left click on the canvas to start the spread.

I ran 273km in five days in the G2G Ultra Marathon! A self-supported foot race along the edge of the grand canyon. I've also run the Canadian Death Race, Al Andalus Ultimate Trail, Blackfoot Ultra, Bad Beaver Ultra, and Midnight Moose.

Contact

Reach out to me on Twitter or by email !