Binary Search

162. Find Peak Element

class Solution {
public:
    void sol(vector<int>& nums, int s, int e, int& res, int& index) {
        if(s >= e) {
            if(res < nums[s]) {
                res = nums[s];
                index = s;
            }
            return;
        }
        int mid = s +(e-s)/2;
        sol(nums, s, mid, res, index);
        sol(nums, mid+1, e, res, index);
    }

    int findPeakElement(vector<int>& nums) {
        int res = INT_MIN;
        int i = 0;
        sol(nums, 0, nums.size()-1, res, i);
        return i;
    }
};

1456. Maximum Number of Vowels in a Substring of Given Length

TLE - 102 / 106

class Solution {
public:
    bool checkVowels(char ch) {
        return (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u');
    }

    int maxVowels(string s, int k) {
        int count = 0;
        int res = 0;

        for(int i = 0; i <= s.size()-k; i++) {
            count = 0;
            int j = i;
            while(j < i+k ){
                if(checkVowels(s[j])) count++;
                j++;
            }
            res = max(res, count);
        }
        return res;
    }
};

Memory Limit Exceed - 80/106 (TC Optimized Sol.)

class Solution {
public:
    bool checkVowels(char ch) {
        return (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u');
    }
    void sol(string str, int s, int e, int& count) {
        if(s >= e) {
            if(checkVowels(str[s])) {
                count++;
            }
            return;
        }
        int mid = s +(e-s)/2;
        sol(str, s, mid, count);
        sol(str, mid+1, e, count);
    }

    int maxVowels(string s, int k) {
        int count = 0;
        int res = 0;

        for(int i = 0; i <= s.size()-k; i++) {
            count = 0;
            sol(s, i, i+k-1, count);
            res = max(res, count);
        }
        return res;
    }
};