java: add «2337. Move Pieces to Obtain a String»

URL:	https://leetcode.com/problems/move-pieces-to-obtain-a-string/
Signed-off-by: Matej Focko <me@mfocko.xyz>

java/move-pieces-to-obtain-a-string.java

@@ -0,0 +1,54 @@
+class Solution {
+  private int skip(String s, int i) {
+    while (i < s.length() && s.charAt(i) == '_') {
+      ++i;
+    }
+
+    return i;
+  }
+
+  private boolean correctMove(String s, int si, String t, int ti) {
+    if (si >= s.length() || ti >= t.length()) {
+      // check if both are out of bounds
+      return si == s.length() && ti == t.length();
+    }
+
+    // wrong order of the characters
+    if (s.charAt(si) != t.charAt(ti)) {
+      return false;
+    }
+
+    // left has to move right
+    if (t.charAt(ti) == 'L' && si < ti) {
+      return false;
+    }
+
+    // right has to move left
+    if (t.charAt(ti) == 'R' && si > ti) {
+      return false;
+    }
+
+    // no issue has been found
+    return true;
+  }
+
+  public boolean canChange(String start, String target) {
+    int i = 0, j = 0;
+    while (i < start.length() && j < target.length()) {
+      i = skip(start, i);
+      j = skip(target, j);
+
+      if (!correctMove(start, i, target, j)) {
+        return false;
+      }
+
+      ++i;
+      ++j;
+    }
+
+    i = skip(start, i);
+    j = skip(target, j);
+
+    return i == start.length() && j == target.length();
+  }
+}