LeetCode 1538: Guess the Majority in a Hidden Array Solution
Master LeetCode problem 1538 (Guess the Majority in a Hidden Array), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.
1538. Guess the Majority in a Hidden Array
Problem Explanation
Explanation
The problem requires us to guess the majority element in a hidden array. We are given a guess() function that takes an index i and returns 1 if the majority element is at index i, -1 if the majority element is less than the element at index i, and 0 if the majority element is greater than the element at index i.
To solve this problem, we can use a binary search approach. We can start by guessing the majority element at the mid index of the array. Based on the result of the guess() function, we can narrow down our search to the left or right half of the array.
The majority element will occupy at least half of the array since it appears more than n/2 times, where n is the length of the array. By using the binary search approach, we can find the majority element in logarithmic time complexity.
Solution Code
class Solution {
public int guessMajority(ArrayReader reader) {
int n = reader.length();
int candidate = reader.get(0);
int count = 1;
for (int i = 1; i < n; i++) {
if (count == 0) {
candidate = reader.get(i);
count = 1;
} else if (reader.get(i) == candidate) {
count++;
} else {
count--;
}
}
count = 0;
for (int i = 0; i < n; i++) {
if (reader.get(i) == candidate) {
count++;
}
}
if (count > n / 2) {
return candidate;
} else {
return -1;
}
}
}Try It Yourself
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