Today I have done Map Sum Pairs and leetcode's March LeetCoding Challenge with cpp.

Map Sum Pairs

Description

Implement the MapSum class:

• MapSum() Initializes the MapSum object.
• void insert(String key, int val) Inserts the key-val pair into the map. If the key already existed, the original key-value pair will be overridden to the new one.
• int sum(string prefix) Returns the sum of all the pairs' value whose key starts with the prefix.

Example 1:

Input
["MapSum", "insert", "sum", "insert", "sum"]
[[], ["apple", 3], ["ap"], ["app", 2], ["ap"]]
Output
[null, null, 3, null, 5]

Explanation
MapSum mapSum = new MapSum();
mapSum.insert("apple", 3);  
mapSum.sum("ap");           // return 3 (apple = 3)
mapSum.insert("app", 2);    
mapSum.sum("ap");           // return 5 (apple + app = 3 + 2 = 5)

Constraints:

• 1 <= key.length, prefix.length <= 50
• key and prefix consist of only lowercase English letters.
• 1 <= val <= 1000
• At most 50 calls will be made to insert and sum.

Solution

class MapSum {
    unordered_map<string, int> mp;
public:    
    void insert(string key, int val) {
        mp[key] = val;
    }
    
    int sum(string prefix) {
        int result = 0;
        for(auto &[s, v] : mp) {
            if(s.rfind(prefix, 0) == 0) {
                result += v;
            }
        }
        return result;
    }
};

March LeetCoding Challenge 1

Description

Distribute Candies

Alice has n candies, where the ith candy is of type candyType[i]. Alice noticed that she started to gain weight, so she visited a doctor.

The doctor advised Alice to only eat n / 2 of the candies she has (n is always even). Alice likes her candies very much, and she wants to eat the maximum number of different types of candies while still following the doctor's advice.

Given the integer array candyType of length n, return the maximum number of different types of candies she can eat if she only eats n / 2 of them.

Example 1:

Input: candyType = [1,1,2,2,3,3]
Output: 3
Explanation: Alice can only eat 6 / 2 = 3 candies. Since there are only 3 types, she can eat one of each type.

Example 2:

Input: candyType = [1,1,2,3]
Output: 2
Explanation: Alice can only eat 4 / 2 = 2 candies. Whether she eats types [1,2], [1,3], or [2,3], she still can only eat 2 different types.

Example 3:

Input: candyType = [6,6,6,6]
Output: 1
Explanation: Alice can only eat 4 / 2 = 2 candies. Even though she can eat 2 candies, she only has 1 type.

Constraints:

• n == candyType.length

• 2 <= n <= 104

• n is even.

• -105 <= candyType[i] <= 105

Solution

class Solution {
public:
    bool validateStackSequences(vector<int>& pushed, vector<int>& popped) {
        int pos = 0;
        int len = pushed.size();
        vector<int> st;
        for(int i = 0; i < len; ++i) {
            if(st.size() && st.back() == popped[i]) {
                st.pop_back();
                continue;
            }
            while(pos < len && pushed[pos] != popped[i]) {
                st.push_back(pushed[pos]);
                pos += 1;
            }
            if(pos < len && pushed[pos] == popped[i]) {
                pos += 1;
                continue;
            }
            return false;
        }
        return true;
    }
};