Complete "longest common ..." examples (#100)

* no else return

* fix var ref

* fix importing/requiring dependencies

* complete longest common examples

03_recursion/ES6/01_countdown.js

@@ -1,11 +1,11 @@
-const countdown = (i) => {
+const countdown = i => {
   console.log(i);
   // base case
   if (i <= 0) {
-    return null;
+    return;
   }
+
   countdown(i - 1);
-  return null;
 };
 
 countdown(5);

03_recursion/Golang/01_countdown/Countdown.go

@@ -6,9 +6,9 @@ func countdown(i int) {
 	fmt.Println(i)
 	if i <= 0 {
 		return
-	} else {
-		countdown(i - 1)
 	}
+
+	countdown(i - 1)
 }
 
 func main() {

03_recursion/Golang/03_factorial/Factorial.go

@@ -5,9 +5,9 @@ import "fmt"
 func fact(x int) int {
 	if x == 1 {
 		return 1
-	} else {
-		return x * fact(x-1)
 	}
+
+	return x * fact(x-1)
 }
 
 func main() {

03_recursion/javascript/01_countdown.js

@@ -3,9 +3,9 @@ function countdown(i) {
   // base case
   if (i <= 0) {
     return;
-  } else {
-    countdown(i-1);
   }
+
+  countdown(i - 1);
 }
 
 countdown(5);

03_recursion/javascript/03_factorial.js

@@ -1,9 +1,8 @@
 function fact(x) {
   if (x === 1) {
     return 1;
-  } else {
-    return x * fact(x-1);
   }
+  return x * fact(x - 1);
 }
 
 console.log(fact(5));

04_quicksort/ES6/01_loop_sum.js

@@ -3,16 +3,12 @@
  * @param {Array} arr Array of numbers
  * @return {number} Sum of the numbers
  */
-const sumLoop = ( arr ) => {
-    let result = 0;
-
-    for ( let i = 0; i < newArr.length; i++ ) {
-        result += newArr[i];
-    }
-
-    return result;
+const sumLoop = arr => {
+  let result = 0;
+  for (let i = 0; i < arr.length; i++) {
+    result += arr[i];
+  }
+  return result;
 };
 
-let arr = [1, 2, 3, 4];
-
-console.log( sumLoop( arr ) ); // 10
+console.log(sumLoop([1, 2, 3, 4])); // 10

04_quicksort/ES6/01_loop_sum_reduce_version.js

@@ -3,14 +3,6 @@
  * @param {Array} arr Array of numbers
  * @return {number} Sum of the numbers
  */
-const sumReduce = ( arr ) => {
-    let result = newArr.reduce( ( curr, prev ) => {
-        return curr + prev;
-    } );
+const sumReduce = arr => arr.reduce((curr, prev) => curr + prev);
 
-    return result;
-};
-
-let arr = [1, 2, 3, 4];
-
-console.log( sumReduce( arr ) ); // 10
+console.log(sumReduce([1, 2, 3, 4])); // 10

04_quicksort/javascript/01_loop_sum_reduce_version.js

@@ -3,14 +3,10 @@
  * @param {Array} arr Array of numbers
  * @return {number} Sum of the numbers
  */
-function sumReduce( arr ) {
-    var result = newArr.reduce( ( curr, prev ) => {
-        return curr + prev;
-    } );
-
-    return result;
+function sumReduce(arr) {
+  return arr.reduce(function(curr, prev) {
+    return curr + prev;
+  });
 }
 
-var arr = [1, 2, 3, 4];
-
-console.log( sumReduce( arr ) ); // 10
+console.log(sumReduce([1, 2, 3, 4])); // 10

04_quicksort/javascript/02_recursive_sum.js

@@ -1,13 +1,13 @@
-const arr = [1, 2, 3, 4];
-
 /**
  * Sums values in array recursively
  * @param {Array} arr Array of numbers
  * @return {number} Sum of the numbers
  */
-const sumRecursive = ( arr ) => {
-    if ( arr.length == 1 ) return arr[0];
-    return arr[0] + sumRecursive( arr.slice( 1 ) );
-};
+function sumRecursive(arr) {
+  if (arr.length == 1) {
+    return arr[0];
+  }
+  return arr[0] + sumRecursive(arr.slice(1));
+}
 
-console.log( sumRecursive( arr ) );  // 10
+console.log(sumRecursive([1, 2, 3, 4])); // 10

04_quicksort/javascript/05_quicksort.js

@@ -1,18 +1,19 @@
-'use strict';
-
 function quicksort(array) {
   if (array.length < 2) {
     // base case, arrays with 0 or 1 element are already "sorted"
     return array;
-  } else {
-   // recursive case
-   let pivot = array[0];
-   // sub-array of all the elements less than the pivot
-   let less = array.slice(1).filter(function(el) { return el <= pivot; });
-   // sub-array of all the elements greater than the pivot
-   let greater = array.slice(1).filter(function(el) { return el > pivot; });
-   return quicksort(less).concat([pivot], quicksort(greater));
   }
+  // recursive case
+  let pivot = array[0];
+  // sub-array of all the elements less than the pivot
+  let less = array.slice(1).filter(function(el) {
+    return el <= pivot;
+  });
+  // sub-array of all the elements greater than the pivot
+  let greater = array.slice(1).filter(function(el) {
+    return el > pivot;
+  });
+  return quicksort(less).concat([pivot], quicksort(greater));
 }
 
 console.log(quicksort([10, 5, 2, 3])); // [2, 3, 5, 10]

05_hash_tables/ES6/01_price_of_groceries.js

@@ -3,6 +3,6 @@ const book = {};
 book.apple = 0.67;
 // milk costs $1.49
 book.milk = 1.49;
-book.avokado = 1.49;
+book.avocado = 1.49;
 
 console.log(book); // { apple: 0.67, milk: 1.49, avocado: 1.49 }

06_breadth-first_search/Golang/01_breadth-first_search.go

@@ -31,10 +31,11 @@ func search(name string) bool {
 			if person_is_seller(person) {
 				println(person + " is mango seller!")
 				return true
-			} else {
-				search_queue = append(search_queue, graph[person]...)
-				searched = append(searched, person)
 			}
+
+			search_queue = append(search_queue, graph[person]...)
+			searched = append(searched, person)
+
 		}
 	}
 	return false

06_breadth-first_search/golang/bfs.go

@@ -39,10 +39,10 @@ func search(name string) bool {
 			if PersonIsSeller(person) {
 				fmt.Println(person + " is the mango seller!")
 				return true
-			} else {
-				search_queue = append(search_queue, graph[person]...)
-				searched = append(searched, person)
 			}
+
+			search_queue = append(search_queue, graph[person]...)
+			searched = append(searched, person)
 		}
 
 	}

06_breadth-first_search/javascript/01_breadth-first_search.js

@@ -1,7 +1,5 @@
-'use strict';
-
 function person_is_seller(name) {
-  return name[name.length-1] === 'm';
+  return name[name.length - 1] === "m";
 }
 
 const graph = {};
@@ -14,7 +12,6 @@ graph["peggy"] = [];
 graph["thom"] = [];
 graph["jonny"] = [];
 
-
 function search(name) {
   let search_queue = [];
   search_queue = search_queue.concat(graph[name]);
@@ -25,17 +22,16 @@ function search(name) {
     // Only search this person if you haven't already searched them
     if (searched.indexOf(person) === -1) {
       if (person_is_seller(person)) {
-        console.log(person + ' is a mango seller!');
+        console.log(person + " is a mango seller!");
         return true;
-      } else {
-        search_queue = search_queue.concat(graph[person]);
-        // Marks this person as searched
-        searched.push(person);
       }
+
+      search_queue = search_queue.concat(graph[person]);
+      // Marks this person as searched
+      searched.push(person);
     }
   }
   return false;
 }
 
-
-search('you'); // thom is a mango seller!
+search("you"); // thom is a mango seller!

09_dynamic_programming/ES6/01_longest_common_subsequence.js

@@ -1,7 +1,54 @@
-if (word_a[i] === word_b[j]) {
-  // The letters match
-  cell[i][j] = cell[i - 1][j - 1] + 1;
-} else {
-  // The letters don't match
-  cell[i][j] = Math.max(cell[i - 1][j], cell[i][j - 1]);
+function createMatrix(rows, cols) {
+  const matrix = new Array(rows);
+
+  for (let i = 0; i < matrix.length; i++) {
+    matrix[i] = new Array(cols).fill(0);
+  }
+
+  return matrix;
 }
+
+function substring(a, b) {
+  const cell = createMatrix(a.length + 1, b.length + 1);
+  let lcs = 0;
+  let lastSubIndex = 0;
+
+  for (let i = 1; i <= a.length; i++) {
+    for (let j = 1; j <= b.length; j++) {
+      if (a[i - 1] === b[j - 1]) {
+        cell[i][j] = cell[i - 1][j - 1] + 1;
+
+        if (cell[i][j] > lcs) {
+          lcs = cell[i][j];
+          lastSubIndex = i;
+        }
+      } else {
+        cell[i][j] = 0;
+      }
+    }
+  }
+
+  return a.slice(lastSubIndex - lcs, lastSubIndex);
+}
+
+substring("vista", "hish"); // "is"
+substring("fish", "hish"); // "ish"
+
+function subsequence(a, b) {
+  const cell = createMatrix(a.length + 1, b.length + 1);
+
+  for (let i = 1; i <= a.length; i++) {
+    for (let j = 1; j <= b.length; j++) {
+      if (a[i] === b[j]) {
+        cell[i][j] = cell[i - 1][j - 1] + 1;
+      } else {
+        cell[i][j] = Math.max(cell[i - 1][j], cell[i][j - 1]);
+      }
+    }
+  }
+
+  return cell[a.length][b.length];
+}
+
+subsequence("fish", "fosh"); // 3
+subsequence("fort", "fosh"); // 2

09_dynamic_programming/ES6/examples/base.js

@@ -1,9 +1,7 @@
-const initializeMatrix = (rows, cols) => {
+export const initializeMatrix = (rows, cols) => {
   const matrix = [];
   for (let i = 0; i < rows.length; i += 1) {
     matrix.push(Array(cols.length).fill(0));
   }
   return matrix;
 };
-
-export default initializeMatrix;

09_dynamic_programming/ES6/examples/diff_two_words.js

@@ -1,8 +1,8 @@
-import base from './base';
+import { initializeMatrix } from "./base";
 
 const diff = (firstWord, secondWord) => {
-  const arr1 = firstWord.split('');
-  const arr2 = secondWord.split('');
+  const arr1 = firstWord.split("");
+  const arr2 = secondWord.split("");
   const matrix = initializeMatrix(arr1, arr2);
   for (let i = 0; i < arr1.length; i += 1) {
     for (let j = 0; j < arr2.length; j += 1) {

09_dynamic_programming/golang/01_longest_common_subsequence.go

@@ -1,11 +1,53 @@
 package main
 
-import "fmt"
-
-func main() {
-	if word_a[i] == word_b[j] {
-		cell[i][j] = cell[i-1][j-1] + 1
-	} else {
-		cell[i][j] = max(cell[i-1][j], cell[i][j-1])
+func createMatrix(rows, cols int) [][]int {
+	cell := make([][]int, rows)
+	for i := range cell {
+		cell[i] = make([]int, cols)
 	}
+
+	return cell
+}
+
+func substring(a, b string) string {
+	lcs := 0
+	lastSubIndex := 0
+	cell := createMatrix(len(a)+1, len(b)+1)
+
+	for i := 1; i <= len(a); i++ {
+		for j := 1; j <= len(b); j++ {
+			if a[i-1] == b[j-1] {
+				cell[i][j] = cell[i-1][j-1] + 1
+
+				if cell[i][j] > lcs {
+					lcs = cell[i][j]
+					lastSubIndex = i
+				}
+			} else {
+				cell[i][j] = 0
+			}
+		}
+	}
+
+	return a[lastSubIndex-lcs : lastSubIndex]
+}
+
+func subsequence(a, b string) int {
+	cell := createMatrix(len(a)+1, len(b)+1)
+
+	for i := 1; i <= len(a); i++ {
+		for j := 1; j <= len(b); j++ {
+			if a[i-1] == b[j-1] {
+				cell[i][j] = cell[i-1][j-1] + 1
+			} else {
+				cell[i][j] = cell[i-1][j]
+
+				if cell[i][j] < cell[i][j-1] {
+					cell[i][j] = cell[i][j-1]
+				}
+			}
+		}
+	}
+
+	return cell[len(a)][len(b)]
 }

09_dynamic_programming/golang/01_longest_common_subsequence_test.go

@@ -0,0 +1,42 @@
+package main
+
+import "testing"
+
+func TestSubstring(t *testing.T) {
+	var stests = []struct {
+		name, a, b, expected string
+	}{
+		{"hish-vista", "vista", "hish", "is"},
+		{"hish-fish", "fish", "hish", "ish"},
+	}
+
+	for _, tt := range stests {
+		t.Run(tt.name, func(t *testing.T) {
+			actual := substring(tt.a, tt.b)
+
+			if actual != tt.expected {
+				t.Errorf("Expected %s but received %s", tt.expected, actual)
+			}
+		})
+	}
+}
+
+func TestSubsequence(t *testing.T) {
+	var stests = []struct {
+		name, a, b string
+		expected   int
+	}{
+		{"fosh-fish", "fish", "fosh", 3},
+		{"fosh-fort", "fort", "fosh", 2},
+	}
+
+	for _, tt := range stests {
+		t.Run(tt.name, func(t *testing.T) {
+			actual := subsequence(tt.a, tt.b)
+
+			if actual != tt.expected {
+				t.Errorf("Expected %d but received %d", tt.expected, actual)
+			}
+		})
+	}
+}

09_dynamic_programming/javascript/examples/base.js

@@ -1,7 +1,7 @@
-export default function initialize_matrix(rows, cols){
-    let matrix = [];
-    for (let i = 0; i < rows.length; i++){
-        matrix.push(Array(cols.length).fill(0));
-    }
-    return matrix;
-}
+module.exports = function initialize_matrix(rows, cols) {
+  let matrix = [];
+  for (let i = 0; i < rows.length; i++) {
+    matrix.push(Array(cols.length).fill(0));
+  }
+  return matrix;
+};

09_dynamic_programming/javascript/examples/diff_two_words.js

@@ -1,25 +1,25 @@
-import initialize_matrix as base from "./base.js";
+const initialize_matrix = require("./base.js");
 
-export default function diff( firstWord, secondWord ){
-    let arr1 = firstWord.split('');
-    let arr2 = secondWord.split('');
-    let matrix = initialize_matrix(arr1, arr2);
-    for (let i = 0; i < arr1.length; i++){
-        for (let j = 0; j < arr2.length; j++){
-            if( arr1[i] == arr2[j] ){
-                if( i > 0 && j > 0){
-                    matrix[i][j] = matrix[i - 1][j - 1] + 1;
-                }else{
-                    matrix[i][j] = 1;
-                }
-            } else {
-                if( i > 0 && j > 0){
-                    matrix[i][j] = Math.max(matrix[i - 1][j], matrix[i][j - 1]);
-                }else{
-                    matrix[i][j] = 0;
-                }
-            }
+function diff(firstWord, secondWord) {
+  let arr1 = firstWord.split("");
+  let arr2 = secondWord.split("");
+  let matrix = initialize_matrix(arr1, arr2);
+  for (let i = 0; i < arr1.length; i++) {
+    for (let j = 0; j < arr2.length; j++) {
+      if (arr1[i] == arr2[j]) {
+        if (i > 0 && j > 0) {
+          matrix[i][j] = matrix[i - 1][j - 1] + 1;
+        } else {
+          matrix[i][j] = 1;
         }
+      } else {
+        if (i > 0 && j > 0) {
+          matrix[i][j] = Math.max(matrix[i - 1][j], matrix[i][j - 1]);
+        } else {
+          matrix[i][j] = 0;
+        }
+      }
     }
-    return matrix[arr1.length-1][arr2.length-1];
-}
+  }
+  return matrix[arr1.length - 1][arr2.length - 1];
+}

README.md

@@ -14,5 +14,5 @@ This repo also contains every image in Grokking Algorithms, in hi-res. These ima
 
 ## Contributing
 
-- The examples in this book are in Python, but I'd like to get examples in Ruby, Javascript, C, and other languages too. Please add examples in other languages!
+- The examples in this book are in Python, but I'd like to get examples in Ruby, JavaScript, C, and other languages too. Please add examples in other languages!
 - I'm pretty responsive to PRs. That is the quickest way to contribute to this repo.