Day1: Leetcode challenge problem solutions

Solution162.java

class Solution162 {
   /**
   * https://leetcode.com/problems/find-peak-element/
   */
    public int findPeakElement(int[] nums) {
        return search(nums, 0, nums.length - 1);
    }
    public int search(int[] nums, int l, int r) {
        if (l == r)
            return l;
        int mid = (l + r) / 2;
        if (nums[mid] > nums[mid + 1])
            return search(nums, l, mid);
        return search(nums, mid + 1, r);
    }
}

Solution448.java

class Solution448 {
  //448. Find All Numbers Disappeared in an Array 
  /**
  * https://leetcode.com/problems/find-all-numbers-disappeared-in-an-array/
  * Time complexity: O(n) = 2*n
  * Space complexity: O(1) constant space just additional space to return the unvisited elements
  */
  public List<Integer> findDisappearedNumbers(int[] nums) {
      int n = nums.length+1; //as the array elements are from 1 to n so to indicate add pading greater than n.
      //indicate the elements visited by adding n to each visited element
      for (int i: nums) {
        int reali = i % n;
        nums[reali-1] += n;
      }
      
      List<Integer> rlist = new ArrayList<>();
      //now iterate the elements to find any number less than n to indicate we didnt visited 
      for (int i=0; i< n-1;i++) {
        if(nums[i] < n) {
          rlist.add(i+1);
        }
      }
      return rlist;
    }
}

Solution996.java

class Solution996 {
    Set<String> words_perfect;
    Map<String, String> words_cap;
    Map<String, String> words_vow;

    public String[] spellchecker(String[] wordlist, String[] queries) {
        words_perfect = new HashSet();
        words_cap = new HashMap();
        words_vow = new HashMap();

        for (String word: wordlist) {
            words_perfect.add(word);

            String wordlow = word.toLowerCase();
            words_cap.putIfAbsent(wordlow, word);

            String wordlowDV = devowel(wordlow);
            words_vow.putIfAbsent(wordlowDV, word);
        }

        String[] ans = new String[queries.length];
        int t = 0;
        for (String query: queries)
            ans[t++] = solve(query);
        return ans;
    }

    public String solve(String query) {
        if (words_perfect.contains(query))
            return query;

        String queryL = query.toLowerCase();
        if (words_cap.containsKey(queryL))
            return words_cap.get(queryL);

        String queryLV = devowel(queryL);
        if (words_vow.containsKey(queryLV))
            return words_vow.get(queryLV);

        return "";
    }

    public String devowel(String word) {
        StringBuilder ans = new StringBuilder();
        for (char c: word.toCharArray())
            ans.append(isVowel(c) ? '*' : c);
        return ans.toString();
    }

    public boolean isVowel(char c) {
        return (c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u');
    }
}