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

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();
  }
}