Today I have done Throne Inheritance and leetcode's February LeetCoding Challenge with cpp.

Throne Inheritance

Description

A kingdom consists of a king, his children, his grandchildren, and so on. Every once in a while, someone in the family dies or a child is born.

The kingdom has a well-defined order of inheritance that consists of the king as the first member. Let's define the recursive function Successor(x, curOrder), which given a person x and the inheritance order so far, returns who should be the next person after x in the order of inheritance.

Successor(x, curOrder):
    if x has no children or all of x's children are in curOrder:
        if x is the king return null
        else return Successor(x's parent, curOrder)
    else return x's oldest child who's not in curOrder

For example, assume we have a kingdom that consists of the king, his children Alice and Bob (Alice is older than Bob), and finally Alice's son Jack.

1. In the beginning, curOrder will be ["king"].
2. Calling Successor(king, curOrder) will return Alice, so we append to curOrder to get ["king", "Alice"].
3. Calling Successor(Alice, curOrder) will return Jack, so we append to curOrder to get ["king", "Alice", "Jack"].
4. Calling Successor(Jack, curOrder) will return Bob, so we append to curOrder to get ["king", "Alice", "Jack", "Bob"].
5. Calling Successor(Bob, curOrder) will return null. Thus the order of inheritance will be ["king", "Alice", "Jack", "Bob"].

Using the above function, we can always obtain a unique order of inheritance.

Implement the ThroneInheritance class:

• ThroneInheritance(string kingName) Initializes an object of the ThroneInheritance class. The name of the king is given as part of the constructor.
• void birth(string parentName, string childName) Indicates that parentName gave birth to childName.
• void death(string name) Indicates the death of name. The death of the person doesn't affect the Successor function nor the current inheritance order. You can treat it as just marking the person as dead.
• string[] getInheritanceOrder() Returns a list representing the current order of inheritance excluding dead people.

Example 1:

Input
["ThroneInheritance", "birth", "birth", "birth", "birth", "birth", "birth", "getInheritanceOrder", "death", "getInheritanceOrder"]
[["king"], ["king", "andy"], ["king", "bob"], ["king", "catherine"], ["andy", "matthew"], ["bob", "alex"], ["bob", "asha"], [null], ["bob"], [null]]
Output
[null, null, null, null, null, null, null, ["king", "andy", "matthew", "bob", "alex", "asha", "catherine"], null, ["king", "andy", "matthew", "alex", "asha", "catherine"]]

Explanation
ThroneInheritance t= new ThroneInheritance("king"); // order: king
t.birth("king", "andy"); // order: king > andy
t.birth("king", "bob"); // order: king > andy > bob
t.birth("king", "catherine"); // order: king > andy > bob > catherine
t.birth("andy", "matthew"); // order: king > andy > matthew > bob > catherine
t.birth("bob", "alex"); // order: king > andy > matthew > bob > alex > catherine
t.birth("bob", "asha"); // order: king > andy > matthew > bob > alex > asha > catherine
t.getInheritanceOrder(); // return ["king", "andy", "matthew", "bob", "alex", "asha", "catherine"]
t.death("bob"); // order: king > andy > matthew > bob > alex > asha > catherine
t.getInheritanceOrder(); // return ["king", "andy", "matthew", "alex", "asha", "catherine"]

Constraints:

• 1 <= kingName.length, parentName.length, childName.length, name.length <= 15
• kingName, parentName, childName, and name consist of lowercase English letters only.
• All arguments childName and kingName are distinct.
• All name arguments of death will be passed to either the constructor or as childName to birth first.
• For each call to birth(parentName, childName), it is guaranteed that parentName is alive.
• At most 100000 calls will be made to birth and death.
• At most 10 calls will be made to getInheritanceOrder.

Solution

class ThroneInheritance {
    string king;
    int count = 1;
    unordered_map<int, vector<int>> children;
    unordered_map<string, int> revMapping;
    vector<string> mapping;
    vector<bool> dead;
    
    void dfs(vector<string> &result, int cur) {
        if(!dead[cur]) result.push_back(mapping[cur]);
        for(auto child : children[cur]) {
            dfs(result, child);
        }
    }
public:
    ThroneInheritance(string kingName): king(kingName) {
        mapping.push_back(kingName);
        dead.push_back(false);
        revMapping[kingName] = 0;
    }
    
    void birth(string parentName, string childName) {
        mapping.push_back(childName);
        dead.push_back(false);
        revMapping[childName] = count;
        children[revMapping[parentName]].push_back(count);
        count += 1;
        
    }
    
    void death(string name) {
        dead[revMapping[name]] = true;
    }
    
    vector<string> getInheritanceOrder() {
        vector<string> result;
        dfs(result, 0);
        return move(result);
    }
};

February LeetCoding Challenge 4

Description

Longest Harmonious Subsequence

We define a harmonious array as an array where the difference between its maximum value and its minimum value is exactly 1.

Given an integer array nums, return the length of its longest harmonious subsequence among all its possible subsequences.

A subsequence of array is a sequence that can be derived from the array by deleting some or no elements without changing the order of the remaining elements.

Example 1:

Input: nums = [1,3,2,2,5,2,3,7]
Output: 5
Explanation: The longest harmonious subsequence is [3,2,2,2,3].

Example 2:

Input: nums = [1,2,3,4]
Output: 2

Example 3:

Input: nums = [1,1,1,1]
Output: 0

Constraints:

• $1 \le nums.length \le 2 * 10^4$
• $-10^9 \le nums[i] \le 10^9$

Solution

class Solution {
public:
    int findLHS(vector<int>& nums) {
        map<int, int> count;
        for(auto i : nums) count[i] += 1;
        int answer = 0;
        for(auto [num, cnt] : count) {
            if(count.count(num+1)) answer = max(answer, cnt + count[num+1]);
        }
        return answer;
    }
};