Slowest Key Solution Amazon OA 2021

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Slowest Key Solution

A newly designed keypad was tested, where a tester pressed a sequence of n keys, one at a time.

You are given a string keysPressed of length n, where keysPressed[i] was the ith key pressed in the testing sequence, and a sorted list releaseTimes, where releaseTimes[i] was the time the ith key was released. Both arrays are 0-indexed. The 0th key was pressed at the time 0, and every subsequent key was pressed at the exact time the previous key was released.

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The tester wants to know the key of the keypress that had the longest duration. The ithkeypress had a duration of releaseTimes[i] - releaseTimes[i - 1], and the 0th keypress had a duration of releaseTimes[0].

Note that the same key could have been pressed multiple times during the test, and these multiple presses of the same key may not have had the same duration.

Return the key of the keypress that had the longest duration. If there are multiple such keypresses, return the lexicographically largest key of the keypresses.

Example 1:

Input: releaseTimes = [9,29,49,50], keysPressed = "cbcd"
Output: "c"
Explanation: The keypresses were as follows:
Keypress for 'c' had a duration of 9 (pressed at time 0 and released at time 9).
Keypress for 'b' had a duration of 29 - 9 = 20 (pressed at time 9 right after the release of the previous character and released at time 29).
Keypress for 'c' had a duration of 49 - 29 = 20 (pressed at time 29 right after the release of the previous character and released at time 49).
Keypress for 'd' had a duration of 50 - 49 = 1 (pressed at time 49 right after the release of the previous character and released at time 50).
The longest of these was the keypress for 'b' and the second keypress for 'c', both with duration 20.
'c' is lexicographically larger than 'b', so the answer is 'c'.

Example 2:

Input: releaseTimes = [12,23,36,46,62], keysPressed = "spuda"
Output: "a"
Explanation: The keypresses were as follows:
Keypress for 's' had a duration of 12.
Keypress for 'p' had a duration of 23 - 12 = 11.
Keypress for 'u' had a duration of 36 - 23 = 13.
Keypress for 'd' had a duration of 46 - 36 = 10.
Keypress for 'a' had a duration of 62 - 46 = 16.
The longest of these was the keypress for 'a' with duration 16.

Constraints:

  • releaseTimes.length == n
  • keysPressed.length == n
  • 2 <= n <= 1000
  • 1 <= releaseTimes[i] <= 109
  • releaseTimes[i] < releaseTimes[i+1]
  • keysPressed contains only lowercase English letters.

Solution

Program C++

class Solution {
public:
char slowestKey(vector& releaseTimes, string keysPressed) {
releaseTimes.push_back(0);
int idx, size = releaseTimes.size(), max_time = -1;
vector sc(size);

    for(idx = 0; idx < size; idx++)
    {
        int time = releaseTimes[idx] - releaseTimes[(idx + size - 1)%size];
        if(time >= max_time)
        {
            if(time > max_time)
                sc.clear();
            
            max_time = time;
            sc.push_back(keysPressed[idx]); 
        }
    }
    releaseTimes.pop_back();
    sort(sc.begin(), sc.end());
    return sc.back();
}
};

Program Python

  • set up the array with releaseTimes + 1 elements (account for zero in the beggining)
  • iterate and populate the pressed durations
  • iterate over pressed durations and consider
    • longest duration pressed
    • if there is a tie with the current element being iterated and the longest duration, get the largest ord (ascii representation between ord(char) – ord(‘a’))

class Solution:
    def slowestKey(self, releaseTimes: List[int], keysPressed: str) -> str:

        if keysPressed is None: return None 
        if len(keysPressed) == 1: return keysPressed
        
        releaseTimes.insert(0, 0)
        
        pressed_durations = []
        
        for i in range(1, len(releaseTimes)):
            duration_pressed = releaseTimes[i] - releaseTimes[i-1]            
            pressed_durations.append((duration_pressed, i-1))
            
        longest_ord = 0
        longest_duration = float('-inf')
        answer = ""
        
        for duration, i in pressed_durations:
            char = keysPressed[i]
            if duration > longest_duration:
                longest_duration = max(longest_duration, duration)             
                longest_ord = ord(char) - ord('a')
                answer = char
            elif duration == longest_duration:
                current_ord = ord(char) - ord('a')
                if current_ord > longest_ord:
                    longest_ord = max(longest_ord, current_ord)
                    answer = char
                    
        return answer

Program Java

class Solution {
    public char slowestKey(int[] a, String s) {
        int res=-1,max=-1;
        int last=0;
        for(int i=0;i<a.length;i++){
            int time=a[i]-last;
            last=a[i];
            if(time>max){max=time;res=i;}
            if(time==max){if(s.charAt(i)>s.charAt(res)){res=i;}}
        }
        return s.charAt(res);
    }
}

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