{"id":51,"date":"2023-02-23T02:41:07","date_gmt":"2023-02-23T02:41:07","guid":{"rendered":"https:\/\/leopoldo.dev\/blog\/?p=51"},"modified":"2023-02-23T02:42:51","modified_gmt":"2023-02-23T02:42:51","slug":"algorithm-design-techniques-a-guide-to-divide-conquer-recursivity-greedy-algorithms-and-dynamic-programming","status":"publish","type":"post","link":"https:\/\/leopoldo.dev\/blog\/2023\/02\/23\/algorithm-design-techniques-a-guide-to-divide-conquer-recursivity-greedy-algorithms-and-dynamic-programming\/","title":{"rendered":"Algorithm Design Techniques: A Guide to Divide &amp; Conquer, Recursivity, Greedy Algorithms, and Dynamic Programming"},"content":{"rendered":"\n<p>When it comes to algorithm design, there are many techniques that can be used to solve complex problems. In this post, we&#8217;ll explore some of the most common algorithm design techniques: Divide &amp; Conquer, Recursivity, Greedy Algorithms, and Dynamic Programming. We&#8217;ll explain each technique and provide some examples to help illustrate the concepts.<\/p>\n\n\n\n<h2>Divide &amp; Conquer<\/h2>\n\n\n\n<p>The Divide &amp; Conquer algorithm design technique involves breaking a problem down into smaller, more manageable sub-problems, solving each sub-problem independently, and then combining the solutions to form a final solution to the original problem.<\/p>\n\n\n\n<p>A classic example of Divide &amp; Conquer is the Merge Sort algorithm, which sorts an array of elements by dividing the array in half, sorting each half, and then merging the sorted halves.<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code><code>fun mergeSort(array: Array&lt;Int>): Array&lt;Int> {\n    if (array.size &lt;= 1) {\n        return array\n    }\n    val middle = array.size \/ 2\n    val left = array.sliceArray(0 until middle)\n    val right = array.sliceArray(middle until array.size)\n    return merge(mergeSort(left), mergeSort(right))\n}\n\nfun merge(left: Array&lt;Int>, right: Array&lt;Int>): Array&lt;Int> {\n    var i = 0\n    var j = 0\n    val result = mutableListOf&lt;Int>()\n    while (i &lt; left.size &amp;&amp; j &lt; right.size) {\n        if (left&#91;i] &lt; right&#91;j]) {\n            result.add(left&#91;i])\n            i++\n        } else {\n            result.add(right&#91;j])\n            j++\n        }\n    }\n    while (i &lt; left.size) {\n        result.add(left&#91;i])\n        i++\n    }\n    while (j &lt; right.size) {\n        result.add(right&#91;j])\n        j++\n    }\n    return result.toTypedArray()\n}\n<\/code><\/code><\/pre>\n\n\n\n<h2>Recursivity<\/h2>\n\n\n\n<p>Recursivity is a technique that involves solving a problem by breaking it down into smaller instances of the same problem. In other words, a function calls itself to solve a problem.<\/p>\n\n\n\n<p>A classic example of Recursivity is the Fibonacci sequence, which generates the sequence by summing the two previous numbers in the sequence.<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code><code>fun fibonacci(n: Int): Int {\n    if (n == 0) {\n        return 0\n    }\n    if (n == 1) {\n        return 1\n    }\n    return fibonacci(n-1) + fibonacci(n-2)\n}\n<\/code><\/code><\/pre>\n\n\n\n<h2>Greedy Algorithms<\/h2>\n\n\n\n<p>Greedy Algorithms are a technique that involves making the locally optimal choice at each step of a problem to eventually arrive at a globally optimal solution.<\/p>\n\n\n\n<p>A classic example of Greedy Algorithms is the Knapsack problem, which involves filling a knapsack with items of different values and weights to maximize the value of the knapsack.<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>kotlinCopy code<code>fun knapsack(items: List&lt;Item&gt;, capacity: Int): List&lt;Item&gt; {\n    val sortedItems = items.sortedByDescending { it.value \/ it.weight.toDouble() }\n    var remainingCapacity = capacity\n    val selectedItems = mutableListOf&lt;Item&gt;()\n    for (item in sortedItems) {\n        if (item.weight &lt;= remainingCapacity) {\n            remainingCapacity -= item.weight\n            selectedItems.add(item)\n        }\n    }\n    return selectedItems\n}<\/code><\/code><\/pre>\n\n\n\n<h2>Dynamic Programming<\/h2>\n\n\n\n<p>Dynamic Programming is a technique that involves breaking a problem down into smaller, overlapping sub-problems, and storing the solutions to these sub-problems to avoid redundant computations.<\/p>\n\n\n\n<p>A classic example of Dynamic Programming is the Longest Common Subsequence problem, which involves finding the longest subsequence that is present in two given sequences.<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>fun lcs(s1: String, s2: String): String {\n    val m = s1.length\n    val n = s2.length\n    val table = Array(m+1) { IntArray(n+1) }\n    for (i in 0..m) {\n        for (j in 0..n) {\n            if (i == 0 || j == 0) {\n                table&#91;i]&#91;j] = 0\n            } else if (s1&#91;i-1] == s2&#91;j-1]) {\n                table&#91;i]&#91;j] = table&#91;i-1]&#91;j-1] + 1\n            } else {\n                table&#91;i]&#91;j] = max(table&#91;i-1]&#91;j], table&#91;i]&#91;j-1])\n            }\n        }\n    }\n    var i = m\n    var j = n\n    val result = StringBuilder()\n    while (i &gt; 0 &amp;&amp; j &gt; 0) {\n        if (s1&#91;i-1] == s2&#91;j-1]) {\n            result.append(s1&#91;i-1])\n            i--\n            j--\n        } else if (table&#91;i-1]&#91;j] &gt; table&#91;i]&#91;j-1]) {\n            i--\n        } else {\n            j--\n        }\n    }\n    return result.reverse().toString()\n}\n<\/code><\/pre>\n\n\n\n<h2>Conclusion<\/h2>\n\n\n\n<p>These are just a few of the many algorithm design techniques that can be used to solve complex problems. By understanding these techniques and their applications, you can become a more skilled and efficient programmer. Remember that the choice of technique depends on the problem at hand, and that some problems may require a combination of techniques. With practice and experience, you can master these techniques and develop your own problem-solving skills.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>When it comes to algorithm design, there are many techniques that can be used to solve complex problems. In this post, we&#8217;ll explore some of the most common algorithm design techniques: Divide &amp; Conquer, Recursivity,<\/p>\n","protected":false},"author":1,"featured_media":54,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[7],"tags":[],"_links":{"self":[{"href":"https:\/\/leopoldo.dev\/blog\/wp-json\/wp\/v2\/posts\/51"}],"collection":[{"href":"https:\/\/leopoldo.dev\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/leopoldo.dev\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/leopoldo.dev\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/leopoldo.dev\/blog\/wp-json\/wp\/v2\/comments?post=51"}],"version-history":[{"count":2,"href":"https:\/\/leopoldo.dev\/blog\/wp-json\/wp\/v2\/posts\/51\/revisions"}],"predecessor-version":[{"id":53,"href":"https:\/\/leopoldo.dev\/blog\/wp-json\/wp\/v2\/posts\/51\/revisions\/53"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/leopoldo.dev\/blog\/wp-json\/wp\/v2\/media\/54"}],"wp:attachment":[{"href":"https:\/\/leopoldo.dev\/blog\/wp-json\/wp\/v2\/media?parent=51"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/leopoldo.dev\/blog\/wp-json\/wp\/v2\/categories?post=51"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/leopoldo.dev\/blog\/wp-json\/wp\/v2\/tags?post=51"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}