Skip to content

Commit df89a21

Browse files
1 parent 5b4f618 commit df89a21

File tree

5 files changed

+6
-6
lines changed

5 files changed

+6
-6
lines changed

1411/dynamic_programming/intro-to-dp.html

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -6669,7 +6669,7 @@ <h1 id="introduction-to-dynamic-programming">Introduction to Dynamic Programming
66696669
<h2 id="speeding-up-fibonacci-with-dynamic-programming-memoization">Speeding up Fibonacci with Dynamic Programming (Memoization)<a class="headerlink" href="#speeding-up-fibonacci-with-dynamic-programming-memoization" title="Permanent link">&para;</a></h2>
66706670
<p>Our recursive function currently solves fibonacci in exponential time. This means that we can only handle small input values before the problem becomes too difficult. For instance, <span class="arithmatex">$f(29)$</span> results in <em>over 1 million</em> function calls!</p>
66716671
<p>To increase the speed, we recognize that the number of subproblems is only <span class="arithmatex">$O(n)$</span>. That is, in order to calculate <span class="arithmatex">$f(n)$</span> we only need to know <span class="arithmatex">$f(n-1),f(n-2), \dots ,f(0)$</span>. Therefore, instead of recalculating these subproblems, we solve them once and then save the result in a lookup table. Subsequent calls will use this lookup table and immediately return a result, thus eliminating exponential work! </p>
6672-
<p>Each recursive call will check against a lookup table to see if the value has been calculated. This is done in <span class="arithmatex">$O(1)$</span> time. If we have previously calcuated it, return the result, otherwise, we calculate the function normally. The overall runtime is <span class="arithmatex">$O(n)$</span>. This is an enormous improvement over our previous exponential time algorithm!</p>
6672+
<p>Each recursive call will check against a lookup table to see if the value has been calculated. This is done in <span class="arithmatex">$O(1)$</span> time. If we have previously calculated it, return the result, otherwise, we calculate the function normally. The overall runtime is <span class="arithmatex">$O(n)$</span>. This is an enormous improvement over our previous exponential time algorithm!</p>
66736673
<div class="highlight"><pre><span></span><code><span class="k">const</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">MAXN</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">100</span><span class="p">;</span>
66746674
<span class="kt">bool</span><span class="w"> </span><span class="n">found</span><span class="p">[</span><span class="n">MAXN</span><span class="p">];</span>
66756675
<span class="kt">int</span><span class="w"> </span><span class="n">memo</span><span class="p">[</span><span class="n">MAXN</span><span class="p">];</span>
@@ -6818,7 +6818,7 @@ <h2 id="dp-contests">DP Contests<a class="headerlink" href="#dp-contests" title=
68186818

68196819
<ul class="metadata page-metadata" data-bi-name="page info" lang="en-us" dir="ltr">
68206820
<span class="contributors-text">Contributors:</span>
6821-
<ul class="contributors" data-bi-name="contributors"><li><a href="https://github.com/mhayter" title="mhayter" data-bi-name="contributorprofile" target="_blank">mhayter</a> (78.18%)</li><li><a href="https://github.com/Zyad-Ayad" title="Zyad-Ayad" data-bi-name="contributorprofile" target="_blank">Zyad-Ayad</a> (9.7%)</li><li><a href="https://github.com/clumsy" title="clumsy" data-bi-name="contributorprofile" target="_blank">clumsy</a> (5.45%)</li><li><a href="https://github.com/ShubhamPhapale" title="ShubhamPhapale" data-bi-name="contributorprofile" target="_blank">ShubhamPhapale</a> (1.82%)</li><li><a href="https://github.com/konstantinosalatzas" title="konstantinosalatzas" data-bi-name="contributorprofile" target="_blank">konstantinosalatzas</a> (1.21%)</li><li><a href="https://github.com/Ahmed-Elshitehi" title="Ahmed-Elshitehi" data-bi-name="contributorprofile" target="_blank">Ahmed-Elshitehi</a> (1.21%)</li><li><a href="https://github.com/jakobkogler" title="jakobkogler" data-bi-name="contributorprofile" target="_blank">jakobkogler</a> (1.21%)</li><li><a href="https://github.com/tj91" title="tj91" data-bi-name="contributorprofile" target="_blank">tj91</a> (0.61%)</li><li><a href="https://github.com/adamant-pwn" title="adamant-pwn" data-bi-name="contributorprofile" target="_blank">adamant-pwn</a> (0.61%)</li></ul>
6821+
<ul class="contributors" data-bi-name="contributors"><li><a href="https://github.com/mhayter" title="mhayter" data-bi-name="contributorprofile" target="_blank">mhayter</a> (78.18%)</li><li><a href="https://github.com/Zyad-Ayad" title="Zyad-Ayad" data-bi-name="contributorprofile" target="_blank">Zyad-Ayad</a> (9.7%)</li><li><a href="https://github.com/clumsy" title="clumsy" data-bi-name="contributorprofile" target="_blank">clumsy</a> (4.85%)</li><li><a href="https://github.com/konstantinosalatzas" title="konstantinosalatzas" data-bi-name="contributorprofile" target="_blank">konstantinosalatzas</a> (1.82%)</li><li><a href="https://github.com/ShubhamPhapale" title="ShubhamPhapale" data-bi-name="contributorprofile" target="_blank">ShubhamPhapale</a> (1.82%)</li><li><a href="https://github.com/Ahmed-Elshitehi" title="Ahmed-Elshitehi" data-bi-name="contributorprofile" target="_blank">Ahmed-Elshitehi</a> (1.21%)</li><li><a href="https://github.com/jakobkogler" title="jakobkogler" data-bi-name="contributorprofile" target="_blank">jakobkogler</a> (1.21%)</li><li><a href="https://github.com/tj91" title="tj91" data-bi-name="contributorprofile" target="_blank">tj91</a> (0.61%)</li><li><a href="https://github.com/adamant-pwn" title="adamant-pwn" data-bi-name="contributorprofile" target="_blank">adamant-pwn</a> (0.61%)</li></ul>
68226822
</ul>
68236823

68246824
</article>

0 commit comments

Comments
 (0)
pFad - Phonifier reborn

Pfad - The Proxy pFad of © 2024 Garber Painting. All rights reserved.

Note: This service is not intended for secure transactions such as banking, social media, email, or purchasing. Use at your own risk. We assume no liability whatsoever for broken pages.


Alternative Proxies:

Alternative Proxy

pFad Proxy

pFad v3 Proxy

pFad v4 Proxy