java: add «2370. Longest Ideal Subsequence»

Signed-off-by: Matej Focko <me@mfocko.xyz>

java/longest-ideal-subsequence.java

@@ -0,0 +1,24 @@
+class Solution {
+  public int longestIdealString(String s, int k) {
+    int[] lengths = new int[26];
+
+    int longest = 0;
+    for (int i = 0; i < s.length(); ++i) {
+      int c = s.charAt(i) - 'a';
+
+      int longestIncluding = 0;
+      for (int pred = 0; pred < 26; ++pred) {
+        if (Math.abs(pred - c) > k) {
+          continue;
+        }
+
+        longestIncluding = Math.max(longestIncluding, lengths[pred]);
+      }
+
+      lengths[c] = Math.max(lengths[c], longestIncluding + 1);
+      longest = Math.max(longest, lengths[c]);
+    }
+
+    return longest;
+  }
+}