Tasks Details
easy
1.
EquiLeader
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.
Task Score
100%
Correctness
100%
Performance
100%
A non-empty 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] = 2we 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 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] = 2the function should return 2, as explained above.
Write an efficient algorithm for the following assumptions:
- 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].
Copyright 2009–2025 by Codility Limited. All Rights Reserved. Unauthorized copying, publication or disclosure prohibited.
Solution
Programming language used Java 8
Time spent on task 52 minutes
Notes
not defined yet
Code: 17:05:29 UTC,
java,
verify,
result: Failed
// you can also use imports, for example:
import java.util.*;
// you can use System.out.println for debugging purposes, e.g.
// System.out.println("this is a debug message");
class Solution {
public int solution(int[] A) {
int size = 0;
int value = 0;
for (int i=0; i<A.length; i++) {
if (size == 0) {
size++;
value = A[i];
} else {
if (A[i] == value)
size++;
else
size--;
}
}
int count = 0;
for (int j=0; j<A.length; j++) {
if (A[j] == value) {
count++;
}
}
if (count <= (A.length/2)) {
return 0;
} else {
int indices = 0;
size = 0;
for (int k=0; k<A.length-1; k++) {
if (A[k] == value){
count--;
size++;
}
if (size > ((k+1)/2)) && (count > (A.length-(k+1))/2 ) {
indices++;
}
}
return indices;
}
}
}
Analysis
Compile error
Solution.java:43: error: illegal start of expression
if (size > ((k+1)/2)) && (count > (A.length-(k+1))/2 ) {
^
Solution.java:43: error: ';' expected
if (size > ((k+1)/2)) && (count > (A.length-(k+1))/2 ) {
^
2 errors
Code: 17:05:54 UTC,
java,
verify,
result: Passed
// you can also use imports, for example:
import java.util.*;
// you can use System.out.println for debugging purposes, e.g.
// System.out.println("this is a debug message");
class Solution {
public int solution(int[] A) {
int size = 0;
int value = 0;
for (int i=0; i<A.length; i++) {
if (size == 0) {
size++;
value = A[i];
} else {
if (A[i] == value)
size++;
else
size--;
}
}
int count = 0;
for (int j=0; j<A.length; j++) {
if (A[j] == value) {
count++;
}
}
if (count <= (A.length/2)) {
return 0;
} else {
int indices = 0;
size = 0;
for (int k=0; k<A.length-1; k++) {
if (A[k] == value){
count--;
size++;
}
if ((size > ((k+1)/2)) && (count > (A.length-(k+1))/2 )) {
indices++;
}
}
return indices;
}
}
}
Analysis
Code: 17:06:06 UTC,
java,
verify,
result: Passed
// you can also use imports, for example:
import java.util.*;
// you can use System.out.println for debugging purposes, e.g.
// System.out.println("this is a debug message");
class Solution {
public int solution(int[] A) {
int size = 0;
int value = 0;
for (int i=0; i<A.length; i++) {
if (size == 0) {
size++;
value = A[i];
} else {
if (A[i] == value)
size++;
else
size--;
}
}
int count = 0;
for (int j=0; j<A.length; j++) {
if (A[j] == value) {
count++;
}
}
if (count <= (A.length/2)) {
return 0;
} else {
int indices = 0;
size = 0;
for (int k=0; k<A.length-1; k++) {
if (A[k] == value){
count--;
size++;
}
if ((size > ((k+1)/2)) && (count > (A.length-(k+1))/2 )) {
indices++;
}
}
return indices;
}
}
}
User test case 1:
None
Analysis
Code: 17:06:34 UTC,
java,
verify,
result: Passed
// you can also use imports, for example:
import java.util.*;
// you can use System.out.println for debugging purposes, e.g.
// System.out.println("this is a debug message");
class Solution {
public int solution(int[] A) {
int size = 0;
int value = 0;
for (int i=0; i<A.length; i++) {
if (size == 0) {
size++;
value = A[i];
} else {
if (A[i] == value)
size++;
else
size--;
}
}
int count = 0;
for (int j=0; j<A.length; j++) {
if (A[j] == value) {
count++;
}
}
if (count <= (A.length/2)) {
return 0;
} else {
int indices = 0;
size = 0;
for (int k=0; k<A.length-1; k++) {
if (A[k] == value){
count--;
size++;
}
if ((size > ((k+1)/2)) && (count > (A.length-(k+1))/2 )) {
indices++;
}
}
return indices;
}
}
}
User test case 1:
None
Analysis
Code: 17:06:50 UTC,
java,
verify,
result: Passed
// you can also use imports, for example:
import java.util.*;
// you can use System.out.println for debugging purposes, e.g.
// System.out.println("this is a debug message");
class Solution {
public int solution(int[] A) {
int size = 0;
int value = 0;
for (int i=0; i<A.length; i++) {
if (size == 0) {
size++;
value = A[i];
} else {
if (A[i] == value)
size++;
else
size--;
}
}
int count = 0;
for (int j=0; j<A.length; j++) {
if (A[j] == value) {
count++;
}
}
if (count <= (A.length/2)) {
return 0;
} else {
int indices = 0;
size = 0;
for (int k=0; k<A.length-1; k++) {
if (A[k] == value){
count--;
size++;
}
if ((size > ((k+1)/2)) && (count > (A.length-(k+1))/2 )) {
indices++;
}
}
return indices;
}
}
}
User test case 1:
None
Analysis
Code: 17:07:04 UTC,
java,
verify,
result: Passed
// you can also use imports, for example:
import java.util.*;
// you can use System.out.println for debugging purposes, e.g.
// System.out.println("this is a debug message");
class Solution {
public int solution(int[] A) {
int size = 0;
int value = 0;
for (int i=0; i<A.length; i++) {
if (size == 0) {
size++;
value = A[i];
} else {
if (A[i] == value)
size++;
else
size--;
}
}
int count = 0;
for (int j=0; j<A.length; j++) {
if (A[j] == value) {
count++;
}
}
if (count <= (A.length/2)) {
return 0;
} else {
int indices = 0;
size = 0;
for (int k=0; k<A.length-1; k++) {
if (A[k] == value){
count--;
size++;
}
if ((size > ((k+1)/2)) && (count > (A.length-(k+1))/2 )) {
indices++;
}
}
return indices;
}
}
}
User test case 1:
None
Analysis
Code: 17:07:18 UTC,
java,
verify,
result: Passed
// you can also use imports, for example:
import java.util.*;
// you can use System.out.println for debugging purposes, e.g.
// System.out.println("this is a debug message");
class Solution {
public int solution(int[] A) {
int size = 0;
int value = 0;
for (int i=0; i<A.length; i++) {
if (size == 0) {
size++;
value = A[i];
} else {
if (A[i] == value)
size++;
else
size--;
}
}
int count = 0;
for (int j=0; j<A.length; j++) {
if (A[j] == value) {
count++;
}
}
if (count <= (A.length/2)) {
return 0;
} else {
int indices = 0;
size = 0;
for (int k=0; k<A.length-1; k++) {
if (A[k] == value){
count--;
size++;
}
if ((size > ((k+1)/2)) && (count > (A.length-(k+1))/2 )) {
indices++;
}
}
return indices;
}
}
}
User test case 1:
None
Analysis
Code: 17:07:26 UTC,
java,
final,
score:
100
// you can also use imports, for example:
import java.util.*;
// you can use System.out.println for debugging purposes, e.g.
// System.out.println("this is a debug message");
class Solution {
public int solution(int[] A) {
int size = 0;
int value = 0;
for (int i=0; i<A.length; i++) {
if (size == 0) {
size++;
value = A[i];
} else {
if (A[i] == value)
size++;
else
size--;
}
}
int count = 0;
for (int j=0; j<A.length; j++) {
if (A[j] == value) {
count++;
}
}
if (count <= (A.length/2)) {
return 0;
} else {
int indices = 0;
size = 0;
for (int k=0; k<A.length-1; k++) {
if (A[k] == value){
count--;
size++;
}
if ((size > ((k+1)/2)) && (count > (A.length-(k+1))/2 )) {
indices++;
}
}
return indices;
}
}
}
Analysis summary
The solution obtained perfect score.
Analysis
Detected time complexity:
O(N)