solves longest common subsequence

Author: anishLearnsToCode

README.md

@@ -306,6 +306,7 @@
 | 1133 | 🔒 [Largest Unique Number](https://leetcode.com/problems/largest-unique-number)                                                                           |                                                                                                                                                                                      |                                                                                                                                   |
 | 1134 | 🔒 [Armstrong Number](https://leetcode.com/problems/armstrong-number)                                                                                     |                                                                                                                                                                                      |                                                                                                                                   |
 | 1137 | [Nth Tribonacci Number](https://leetcode.com/problems/n-th-tribonacci-number)                                                                             |                                                               [![Java](assets/java.png)](src/NthTribonacciNumber.java)                                                               |                                                                                                                                   |
+| 1143 | [Longest Common Subsequence](https://leetcode.com/problems/longest-common-subsequence)                                                                             |                                                            [![Java](assets/java.png)](src/LongestCommonSubsequence.java)                                                             |                                                                                                                                   |
 | 1150 | [Check if Number is Majority Element in Sorted Array](https://leetcode.com/problems/check-if-a-number-is-majority-element-in-a-sorted-array)              |                                                                                                                                                                                      |                                                                                                                                   |
 | 1154 | [Day of The Year](https://leetcode.com/problems/day-of-the-year)                                                                                          |                                                                  [![Java](assets/java.png)](src/DayOfTheYear.java)                                                                   |                                                                                                                                   |
 | 1160 | [Find Words That Can Be Formed By Characters](https://leetcode.com/problems/find-words-that-can-be-formed-by-characters)                                  |                                                                                                                                                                                      |                                                                                                                                   |

src/LongestCommonSubsequence.java

@@ -0,0 +1,39 @@
+public class LongestCommonSubsequence {
+    public int longestCommonSubsequence(String text1, String text2) {
+        final int[][] memory = new int[2][text2.length()];
+        final int rows = text1.length(), columns = text2.length();
+
+        // first row, first column
+        memory[0][0] = text1.charAt(0) == text2.charAt(0) ? 1 : 0;
+
+        // first row
+        for (int column = 1 ; column < columns ; column++) {
+            memory[0][column] = text2.charAt(column) == text1.charAt(0) ? 1 : memory[0][column - 1];
+        }
+
+        int i = 1;
+        // rest of table
+        for (int row = 1 ; row < rows ; row++, i ^= 1) {
+            for (int column = 0 ; column < text2.length() ; column++) {
+                if (column == 0) {
+                    memory[i][column] = text1.charAt(row) == text2.charAt(0) ? 1 : memory[i ^ 1][column];
+                } else {
+                    memory[i][column] = max(
+                            memory[i][column - 1],
+                            memory[i ^ 1][column],
+                            text1.charAt(row) == text2.charAt(column) ? 1 + memory[i ^ 1][column - 1] : 0
+                    );
+                }
+            }
+        }
+        return memory[i ^ 1][columns - 1];
+    }
+
+    private int max(int... values) {
+        int result = 0;
+        for (int value : values) {
+            result = Math.max(result, value);
+        }
+        return result;
+    }
+}