reorg and add code for second edition

11_dynamic_programming/ES6/01_longest_common_subsequence.js

@@ -0,0 +1,78 @@
+/**
+ * Create a matrix
+ * @param {number} rows Number of rows
+ * @param {number} columns ANumber of columns
+ * @returns {Array} Matrix
+ */
+const createMatrix = (rows = 0, columns = 0) => {
+  const matrix = [];
+
+  for (let i = 0; i < rows; i++) {
+    matrix[i] = Array(columns).fill(0);
+  }
+
+  return matrix;
+};
+
+/**
+ * Find the longest substring
+ * @param {string} firstWord First word
+ * @param {string} secondWord Second word
+ * @returns {string} The longest substring
+ */
+const longestSubstring = (firstWord = "", secondWord = "") => {
+  const matrix = JSON.parse(
+    JSON.stringify(createMatrix(firstWord.length, secondWord.length))
+  );
+  let sizeSequence = 0;
+  let indexSequence = 0;
+
+  for (let i = 0; i < firstWord.length; i++) {
+    for (let j = 0; j < secondWord.length; j++) {
+      if (firstWord[i] === secondWord[j]) {
+        matrix[i][j] = (i && j) > 0 ? matrix[i - 1][j - 1] + 1 : 1;
+
+        if (matrix[i][j] >= sizeSequence) {
+          sizeSequence = matrix[i][j];
+          indexSequence = i + 1;
+        }
+      } else {
+        matrix[i][j] = 0;
+      }
+    }
+  }
+
+  return firstWord.slice(indexSequence - sizeSequence, indexSequence);
+};
+
+longestSubstring("vista", "hish"); // "is"
+longestSubstring("fish", "hish"); // "ish"
+
+/**
+ * Find the longest common subsequence
+ * @param {string} firstWord First word
+ * @param {string} secondWord Second word
+ * @returns {number} The longest common subsequence
+ */
+const longestCommonSubsequence = (firstWord = "", secondWord = "") => {
+  const matrix = JSON.parse(
+    JSON.stringify(createMatrix(firstWord.length, secondWord.length))
+  );
+  if (matrix.length === 0 || matrix[0].length === 0) return 0;
+  for (let i = 0; i < firstWord.length; i++) {
+    for (let j = 0; j < secondWord.length; j++) {
+      if (firstWord[i] === secondWord[j]) {
+        matrix[i][j] = (i && j) > 0 ? matrix[i - 1][j - 1] + 1 : 1;
+      } else {
+        matrix[i][j] = Math.max(
+          i > 0 ? matrix[i - 1][j] : 0,
+          j > 0 ? matrix[i][j - 1] : 0
+        );
+      }
+    }
+  }
+  return matrix[firstWord.length - 1][secondWord.length - 1];
+};
+
+longestCommonSubsequence("fish", "fosh"); // 3
+longestCommonSubsequence("fort", "fosh"); // 2