Match Substring After Replacement LeetCode solution in Java

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class Solution {
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  public boolean matchReplacement(String s, String sub, char[][] mappings) {
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    HashMap<Character, HashSet<Character>> m = new HashMap<>();
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    for (char[] carr : mappings) {
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      if (!m.containsKey(carr[0])) {
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        m.put(carr[0], new HashSet<Character>());
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      }
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      m.get(carr[0]).add(carr[1]);
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    }
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    int len_s = s.length();
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    int len_sub = sub.length();
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    for (int pos = 0; pos < s.length(); pos++) {
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      int i = pos;
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      int j = 0;
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      boolean cont = false;
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      while (j <= sub.length()) {
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        if (j == sub.length()) return true;
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        int lenlefts = len_s - i;
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        int lenleftsub = len_sub - j;
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        if (lenlefts < lenleftsub) {
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          break;
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        } else if ((s.charAt(i) == sub.charAt(j))
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            || (m.containsKey(sub.charAt(j)) && m.get(sub.charAt(j)).contains(s.charAt(i)))) {
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          i += 1;
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          j += 1;
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        } else {
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          break;
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        }
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      }
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    }
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    return false;
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  }
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}