Find the index S such that the leaders of the sequences A[0], A[1], ..., A[S] and A[S + 1], A[S + 2], ..., A[N - 1] are the same.

EquiLeader.java

import java.util.Stack;

public class EquiLeader {
	public int solution(int[] A) {
		if(A == null || A.length == 0) {
			return 0;
		}
		
		Stack<Integer> stack = new Stack<>();
		for(int i = 0; i < A.length; i++) {
			if(stack.isEmpty()) {
				stack.push(A[i]);
				continue;
			}
			
			if(stack.peek() != A[i]) {
				stack.pop();
			} else {
				stack.push(A[i]);
			}
		}
		
		if(stack.isEmpty()) {
			return 0;
		}
		
		int candidate = stack.pop();
		
		int leaderCounter = 0;
		for(int i = 0; i < A.length; i++) {
			if(A[i] == candidate) {
				leaderCounter++;
			}
		}
		
		if(leaderCounter <= A.length / 2) {
			return 0;
		}
		
		int equiLeaders = 0;
		double currentLeaderCount = 0.0;
		
		for(int i = 0; i < A.length; i++) {
			if(A[i] == candidate) {
				currentLeaderCount++;
			}
			
			if(currentLeaderCount > (i + 1.0) / 2.0 && leaderCounter - currentLeaderCount > (A.length - 1.0 - i) / 2.0) {
				equiLeaders++;
			}
		}
		
		return equiLeaders;
	}
}