Codility---EquiLeader

Task description

A non-empty zero-indexed array A consisting of N integers is given.

The leader of this array is the value that occurs in more than half of the elements of A.

An equi leader is an index S such that 0 ≤ S < N − 1 and two sequences A[0], A[1], ..., A[S] and A[S + 1], A[S + 2], ..., A[N − 1] have leaders of the same value.

For example, given array A such that:

A[0] = 4 A[1] = 3 A[2] = 4 A[3] = 4 A[4] = 4 A[5] = 2

we can find two equi leaders:

• 0, because sequences: (4) and (3, 4, 4, 4, 2) have the same leader, whose value is 4.
• 2, because sequences: (4, 3, 4) and (4, 4, 2) have the same leader, whose value is 4.

The goal is to count the number of equi leaders.

Write a function:

class Solution { public int solution(int[] A); }

that, given a non-empty zero-indexed array A consisting of N integers, returns the number of equi leaders.

For example, given:

A[0] = 4 A[1] = 3 A[2] = 4 A[3] = 4 A[4] = 4 A[5] = 2

the function should return 2, as explained above.

Assume that:

• N is an integer within the range [1..100,000];
• each element of array A is an integer within the range [−1,000,000,000..1,000,000,000].

Complexity:

• expected worst-case time complexity is O(N);
• expected worst-case space complexity is O(N), beyond input storage (not counting the storage required for input arguments).

Elements of input arrays can be modified.

Solution

 

Programming language used: Java

Total time used: 26 minutes

 

Code: 02:26:16 UTC, java, final, score:  100

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// you can also use imports, for example:
// import java.util.*;

// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");

class Solution {
    public int solution(int[] A) {
        // write your code in Java SE 8
        int size=0, leader=-1, count=0, fcnt=0, res=0;
        for(int i=0; i<A.length; i++) {
            if(size == 0) {
                leader = A[i];
            }
            if(leader == A[i]) {
                size++;
            } else {
                size--;
            }
        }
        if(size == 0) return 0;
        for(int i=0; i<A.length; i++) {
            if(leader == A[i]) {
                count++;
            }
        }
        for(int i=0; i<A.length; i++) {
            if(leader == A[i] ) {
                fcnt++;
            }
            if((i+1) < fcnt*2 && (A.length-i-1) < (count-fcnt)*2) {
                res++;
            }
        }
        return res;
    }
}

https://codility.com/demo/results/trainingKHWPS7-27V/