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Hash Tables

  • Understanding hash tables
  • Solved problems are presented in alphabetical order
Ransom Note

↗ See LeetCode Problem #383​

import java.util.Map;import java.util.HashMap;public class Solution {    static boolean canConstruct(String ransomNote, String magazine) {        Map<Character, Integer> characterMap = new HashMap<>();        for (int i = 0; i < magazine.length(); i++) {            int characterCount = characterMap.getOrDefault(                    magazine.charAt(i), 0);            characterMap.put(magazine.charAt(i), characterCount + 1);        }        for (int i = 0; i < ransomNote.length(); i++) {            int characterCount = characterMap.getOrDefault(                    ransomNote.charAt(i), 0);            if (characterCount == 0) {                return false;            }            characterMap.put(ransomNote.charAt(i), characterCount - 1);        }        return true;    }    public static void main(String[] args) {        // Example 1:        String ransomNote1 = "a";        String magazine1 = "b";        //  O/P: false        // Example 2:        String ransomNote2 = "aa";        String magazine2 = "ab";        //  O/P: false        // Example 3:        String ransomNote3 = "aa";        String magazine3 = "aab";        //  O/P: true        System.out.println(canConstruct(ransomNote1, magazine1));        System.out.println(canConstruct(ransomNote2, magazine2));        System.out.println(canConstruct(ransomNote3, magazine3));    }}
Two Sum
Two Sum IV - Input is a BST