Tasks Details
easy
1.
PassingCars
Count the number of passing cars on the road.
Task Score
66%
Correctness
100%
Performance
40%
A non-empty array A consisting of N integers is given. The consecutive elements of array A represent consecutive cars on a road.
Array A contains only 0s and/or 1s:
- 0 represents a car traveling east,
- 1 represents a car traveling west.
The goal is to count passing cars. We say that a pair of cars (P, Q), where 0 ≤ P < Q < N, is passing when P is traveling to the east and Q is traveling to the west.
For example, consider array A such that:
A[0] = 0 A[1] = 1 A[2] = 0 A[3] = 1 A[4] = 1We have five pairs of passing cars: (0, 1), (0, 3), (0, 4), (2, 3), (2, 4).
Write a function:
int solution(int A[], int N);
that, given a non-empty array A of N integers, returns the number of pairs of passing cars.
The function should return −1 if the number of pairs of passing cars exceeds 1,000,000,000.
For example, given:
A[0] = 0 A[1] = 1 A[2] = 0 A[3] = 1 A[4] = 1the function should return 5, 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 that can have one of the following values: 0, 1.
Copyright 2009–2024 by Codility Limited. All Rights Reserved. Unauthorized copying, publication or disclosure prohibited.
Solution
Programming language used C
Time spent on task 40 minutes
Notes
not defined yet
Task timeline
Code: 12:40:15 UTC,
c,
verify,
result: Failed
// you can write to stdout for debugging purposes, e.g.
// printf("this is a debug message\n");
int solution(int A[], int N) {
// write your code in C99
long long count =0;
long long[] B = A;
for(long i =1; i<sizeof(B);i++)
{
B[i] += B[i-1];
}
long last = B[sizeof(B)];
for(long i =1; i<sizeof(A);i++)
{
if (A[i]==0)
{
count += last-B[i];
}
}
return count;
}
Analysis
Compile error
func.c: In function 'solution':
func.c:7:14: error: expected identifier or '(' before '[' token
long long[] B = A;
^
func.c:8:29: error: 'B' undeclared (first use in this function)
for(long i =1; i<sizeof(B);i++)
^
func.c:8:29: note: each undeclared identifier is reported only once for each function it appears in
Code: 12:40:34 UTC,
c,
verify,
result: Failed
// you can write to stdout for debugging purposes, e.g.
// printf("this is a debug message\n");
int solution(int A[], int N) {
// write your code in C99
long long count =0;
long long B[] = A;
for(long i =1; i<sizeof(B);i++)
{
B[i] += B[i-1];
}
long last = B[sizeof(B)];
for(long i =1; i<sizeof(A);i++)
{
if (A[i]==0)
{
count += last-B[i];
}
}
return count;
}
Analysis
Compile error
func.c: In function 'solution':
func.c:7:5: error: invalid initializer
long long B[] = A;
^
Code: 12:40:50 UTC,
c,
verify,
result: Failed
// you can write to stdout for debugging purposes, e.g.
// printf("this is a debug message\n");
int solution(int A[], int N) {
// write your code in C99
long long count =0;
long B[] = A;
for(long i =1; i<sizeof(B);i++)
{
B[i] += B[i-1];
}
long last = B[sizeof(B)];
for(long i =1; i<sizeof(A);i++)
{
if (A[i]==0)
{
count += last-B[i];
}
}
return count;
}
Analysis
Compile error
func.c: In function 'solution':
func.c:7:5: error: invalid initializer
long B[] = A;
^
Code: 12:41:21 UTC,
c,
verify,
result: Failed
// you can write to stdout for debugging purposes, e.g.
// printf("this is a debug message\n");
int solution(int A[], int N) {
// write your code in C99
long long count =0;
long B[] ;
B=A;
for(long i =1; i<sizeof(B);i++)
{
B[i] += B[i-1];
}
long last = B[sizeof(B)];
for(long i =1; i<sizeof(A);i++)
{
if (A[i]==0)
{
count += last-B[i];
}
}
return count;
}
Analysis
Compile error
func.c: In function 'solution':
func.c:7:10: error: array size missing in 'B'
long B[] ;
^
func.c:8:6: error: incompatible types when assigning to type 'long int[1]' from type 'int *'
B=A;
^
Code: 12:42:37 UTC,
c,
verify,
result: Failed
// you can write to stdout for debugging purposes, e.g.
// printf("this is a debug message\n");
int solution(int A[], int N) {
// write your code in C99
long long count =0;
long B[sizeof(A)] = A ;
for(long i =1; i<sizeof(B);i++)
{
B[i] += B[i-1];
}
long last = B[sizeof(B)];
for(long i =1; i<sizeof(A);i++)
{
if (A[i]==0)
{
count += last-B[i];
}
}
return count;
}
Analysis
Compile error
func.c: In function 'solution':
func.c:7:5: error: invalid initializer
long B[sizeof(A)] = A ;
^
Code: 12:45:32 UTC,
c,
verify,
result: Failed
// you can write to stdout for debugging purposes, e.g.
// printf("this is a debug message\n");
int solution(int A[], int N) {
// write your code in C99
long long count =0;
long B[sizeof(A)] ;
B = (long)A;
for(long i =1; i<sizeof(B);i++)
{
B[i] += B[i-1];
}
long last = B[sizeof(B)];
for(long i =1; i<sizeof(A);i++)
{
if (A[i]==0)
{
count += last-B[i];
}
}
return count;
}
Analysis
Compile error
func.c: In function 'solution':
func.c:8:7: error: incompatible types when assigning to type 'long int[8]' from type 'long int'
B = (long)A;
^
Code: 12:45:46 UTC,
c,
verify,
result: Failed
// you can write to stdout for debugging purposes, e.g.
// printf("this is a debug message\n");
int solution(int A[], int N) {
// write your code in C99
long long count =0;
long B[sizeof(A)] ;
B = A;
for(long i =1; i<sizeof(B);i++)
{
B[i] += B[i-1];
}
long last = B[sizeof(B)];
for(long i =1; i<sizeof(A);i++)
{
if (A[i]==0)
{
count += last-B[i];
}
}
return count;
}
Analysis
Compile error
func.c: In function 'solution':
func.c:8:7: error: incompatible types when assigning to type 'long int[8]' from type 'int *'
B = A;
^
Code: 12:48:06 UTC,
cs,
verify,
result: Failed
using System;
// you can also use other imports, for example:
// using System.Collections.Generic;
// you can use Console.WriteLine for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution {
public int solution(int[] A) {
// write your code in C# 6.0 with .NET 4.5 (Mono)
long long count =0;
long B[sizeof(A)] ;
B = A;
for(long i =1; i<sizeof(B);i++)
{
B[i] += B[i-1];
}
long last = B[sizeof(B)];
for(long i =1; i<sizeof(A);i++)
{
if (A[i]==0)
{
count += last-B[i];
}
}
}
}
Analysis
Compile error
Compilation failed: 2 error(s), 0 warnings Solution.cs(11,13): error CS1525: Unexpected symbol `long' Solution.cs(12,11): error CS0650: Syntax error, bad array declarator. To declare a managed array the rank specifier precedes the variable's identifier. To declare a fixed size buffer field, use the fixed keyword before the field type
Code: 12:48:26 UTC,
cs,
verify,
result: Failed
using System;
// you can also use other imports, for example:
// using System.Collections.Generic;
// you can use Console.WriteLine for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution {
public int solution(int[] A) {
// write your code in C# 6.0 with .NET 4.5 (Mono)
long count =0;
long B[sizeof(A)] ;
B = A;
for(long i =1; i<sizeof(B);i++)
{
B[i] += B[i-1];
}
long last = B[sizeof(B)];
for(long i =1; i<sizeof(A);i++)
{
if (A[i]==0)
{
count += last-B[i];
}
}
}
}
Analysis
Compile error
Compilation failed: 1 error(s), 0 warnings Solution.cs(12,11): error CS0650: Syntax error, bad array declarator. To declare a managed array the rank specifier precedes the variable's identifier. To declare a fixed size buffer field, use the fixed keyword before the field type
Code: 12:48:44 UTC,
cs,
verify,
result: Failed
using System;
// you can also use other imports, for example:
// using System.Collections.Generic;
// you can use Console.WriteLine for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution {
public int solution(int[] A) {
// write your code in C# 6.0 with .NET 4.5 (Mono)
long count =0;
long B[A.Length] ;
B = A;
for(long i =1; i<sizeof(B);i++)
{
B[i] += B[i-1];
}
long last = B[sizeof(B)];
for(long i =1; i<sizeof(A);i++)
{
if (A[i]==0)
{
count += last-B[i];
}
}
}
}
Analysis
Compile error
Compilation failed: 1 error(s), 0 warnings Solution.cs(12,11): error CS0650: Syntax error, bad array declarator. To declare a managed array the rank specifier precedes the variable's identifier. To declare a fixed size buffer field, use the fixed keyword before the field type
Code: 12:50:40 UTC,
c,
verify,
result: Failed
// you can write to stdout for debugging purposes, e.g.
// printf("this is a debug message\n");
int solution(int A[], int N) {
// write your code in C99
long long count =0;
for(long i =1; i<sizeof(A);i++)
{
A[i] += A[i-1];
}
long last = A[sizeof(A)];
for(long i =1; i<sizeof(A);i++)
{
if (A[i]!=A[i-1])
{
count += last-A[i-1];
}
}
return count;
}
Analysis
expand all
Example tests
1.
0.007 s
RUNTIME ERROR,
tested program terminated unexpectedly
stderr:
Segmentation Fault
Code: 12:51:36 UTC,
c,
verify,
result: Failed
// you can write to stdout for debugging purposes, e.g.
// printf("this is a debug message\n");
int solution(int A[], int N) {
// write your code in C99
long long count =0;
for(long i =1; i<sizeof(A);i++)
{
A[i] += A[i-1];
}
long last = A[sizeof(A)-1];
for(long i =1; i<sizeof(A);i++)
{
if (A[i]!=A[i-1])
{
count += last-A[i-1];
}
}
return count;
}
Analysis
expand all
Example tests
1.
0.006 s
RUNTIME ERROR,
tested program terminated unexpectedly
stderr:
Segmentation Fault
Code: 12:52:54 UTC,
c,
verify,
result: Failed
// you can write to stdout for debugging purposes, e.g.
// printf("this is a debug message\n");
int solution(int A[], int N) {
// write your code in C99
long long count =0;
for(long i =1; i<N;i++)
{
A[i] += A[i-1];
}
long last = A[N-1];
for(long i =1; i<N;i++)
{
if (A[i]!=A[i-1])
{
count += last-A[i-1];
}
}
return count;
}
Analysis
expand all
Example tests
1.
0.006 s
WRONG ANSWER,
got 6 expected 5
Code: 12:56:20 UTC,
c,
verify,
result: Failed
// you can write to stdout for debugging purposes, e.g.
// printf("this is a debug message\n");
int solution(int A[], int N) {
// write your code in C99
long long count =0;
for(long i =1; i<N;i++)
{
A[i] += A[i-1];
}
long last = A[N-1];
for(long i =1; i<N;i++)
{
if (A[i]!=A[i-1])
{
count += last-A[i-1];
}
}
return count;
}
User test case 1:
[0, 0, 1, 1, 0, 0, 1]
Analysis
expand all
Example tests
1.
0.006 s
WRONG ANSWER,
got 6 expected 5
Code: 12:58:24 UTC,
c,
verify,
result: Failed
// you can write to stdout for debugging purposes, e.g.
// printf("this is a debug message\n");
int solution(int A[], int N) {
// write your code in C99
long long count =0;
int B[] = A[];
for(long i =1; i<N;i++)
{
A[i] += A[i-1];
}
long last = A[N-1];
for(long i =1; i<N;i++)
{
if (A[i]!=A[i-1])
{
count += last-A[i-1];
}
}
return count;
}
Analysis
Compile error
func.c: In function 'solution':
func.c:7:17: error: expected expression before ']' token
int B[] = A[];
^
func.c:7:9: warning: unused variable 'B' [-Wunused-variable]
int B[] = A[];
^
Code: 13:05:35 UTC,
c,
verify,
result: Failed
// you can write to stdout for debugging purposes, e.g.
// printf("this is a debug message\n");
int solution(int A[], int N) {
// write your code in C99
long long count =0;
bool B[N];
B[0] = (bool)A[0];
for(long i =1; i<N;i++)
{
B[i]=(bool)A[i];
A[i] += A[i-1];
}
long last = A[N-1];
for(long i =0; i<N;i++)
{
if (B[i])
{
count += last-A[i];
}
}
return count;
}
Analysis
Compile error
func.c: In function 'solution':
func.c:7:5: error: unknown type name 'bool'
bool B[N];
^
func.c:8:13: error: 'bool' undeclared (first use in this function)
B[0] = (bool)A[0];
^
func.c:8:13: note: each undeclared identifier is reported only once for each function it appears in
func.c:8:18: error: expected ';' before 'A'
B[0] = (bool)A[0];
^
func.c:11:20: error: expected ';' before 'A'
B[i]=(bool)A[i];
^
Code: 13:07:33 UTC,
c,
verify,
result: Failed
// you can write to stdout for debugging purposes, e.g.
// printf("this is a debug message\n");
#include <iostream>
#include <string>
#include <cstdlib>
using namespace std;
int solution(int A[], int N) {
// write your code in C99
long long count =0;
bool B[N];
B[0] = (bool)A[0];
for(long i =1; i<N;i++)
{
B[i]=(bool)A[i];
A[i] += A[i-1];
}
long last = A[N-1];
for(long i =0; i<N;i++)
{
if (B[i])
{
count += last-A[i];
}
}
return count;
}
Analysis
Compile error
func.c:3:21: fatal error: iostream: No such file or directory
#include <iostream>
^
compilation terminated.
Code: 13:07:56 UTC,
c,
verify,
result: Failed
// you can write to stdout for debugging purposes, e.g.
printf("this is a debug message\n");
#include <string>
#include <cstdlib>
using namespace std;
int solution(int A[], int N) {
// write your code in C99
long long count =0;
bool B[N];
B[0] = (bool)A[0];
for(long i =1; i<N;i++)
{
B[i]=(bool)A[i];
A[i] += A[i-1];
}
long last = A[N-1];
for(long i =0; i<N;i++)
{
if (B[i])
{
count += last-A[i];
}
}
return count;
}
Analysis
Compile error
func.c:2:9: error: expected declaration specifiers or '...' before string constant
printf("this is a debug message\n");
^
func.c:4:18: fatal error: string: No such file or directory
#include <string>
^
compilation terminated.
Code: 13:08:28 UTC,
c,
verify,
result: Failed
// you can write to stdout for debugging purposes, e.g.
#include <string>
#include <cstdlib>
using namespace std;
int solution(int A[], int N) {
// write your code in C99
printf("this is a debug message\n");
long long count =0;
bool B[N];
B[0] = (bool)A[0];
for(long i =1; i<N;i++)
{
B[i]=(bool)A[i];
A[i] += A[i-1];
}
long last = A[N-1];
for(long i =0; i<N;i++)
{
if (B[i])
{
count += last-A[i];
}
}
return count;
}
Analysis
Compile error
func.c:3:18: fatal error: string: No such file or directory
#include <string>
^
compilation terminated.
Code: 13:08:40 UTC,
c,
verify,
result: Failed
// you can write to stdout for debugging purposes, e.g.
int solution(int A[], int N) {
// write your code in C99
printf("this is a debug message\n");
long long count =0;
bool B[N];
B[0] = (bool)A[0];
for(long i =1; i<N;i++)
{
B[i]=(bool)A[i];
A[i] += A[i-1];
}
long last = A[N-1];
for(long i =0; i<N;i++)
{
if (B[i])
{
count += last-A[i];
}
}
return count;
}
Analysis
Compile error
func.c: In function 'solution':
func.c:8:5: error: unknown type name 'bool'
bool B[N];
^
func.c:9:13: error: 'bool' undeclared (first use in this function)
B[0] = (bool)A[0];
^
func.c:9:13: note: each undeclared identifier is reported only once for each function it appears in
func.c:9:18: error: expected ';' before 'A'
B[0] = (bool)A[0];
^
func.c:12:20: error: expected ';' before 'A'
B[i]=(bool)A[i];
^
Code: 13:09:55 UTC,
c,
verify,
result: Failed
// you can write to stdout for debugging purposes, e.g.
int solution(int A[], int N) {
// write your code in C99
printf("this is a debug message\n");
long long count =0;
int B[N];
B[0] = A[0];
for(long i =1; i<N;i++)
{
B[i]=A[i];
A[i] += A[i-1];
}
long last = A[N-1];
for(long i =0; i<N;i++)
{
if (B[i])
{
count += last-A[i];
}
}
return count;
}
User test case 1:
[0, 0, 1, 1, 0, 0, 1]
Analysis
expand all
Example tests
1.
0.007 s
WRONG ANSWER,
got 3 expected 5
stdout:
this is a debug message
expand all
User tests
1.
0.007 s
OK
function result: 3
function result: 3
stdout:
this is a debug message
Code: 13:10:41 UTC,
c,
verify,
result: Passed
// you can write to stdout for debugging purposes, e.g.
int solution(int A[], int N) {
// write your code in C99
printf("this is a debug message\n");
long long count =0;
int B[N];
B[0] = A[0];
for(long i =1; i<N;i++)
{
B[i]=A[i];
A[i] += A[i-1];
}
long last = A[N-1];
for(long i =0; i<N;i++)
{
if (B[i]==0)
{
count += last-A[i];
}
}
return count;
}
User test case 1:
[0, 0, 1, 1, 0, 0, 1]
Analysis
expand all
User tests
1.
0.007 s
OK
function result: 8
function result: 8
stdout:
this is a debug message
Code: 13:11:01 UTC,
c,
verify,
result: Passed
// you can write to stdout for debugging purposes, e.g.
int solution(int A[], int N) {
// write your code in C99
// printf("this is a debug message\n");
long long count =0;
int B[N];
B[0] = A[0];
for(long i =1; i<N;i++)
{
B[i]=A[i];
A[i] += A[i-1];
}
long last = A[N-1];
for(long i =0; i<N;i++)
{
if (B[i]==0)
{
count += last-A[i];
}
}
return count;
}
User test case 1:
[0, 0, 1, 1, 0, 0, 1]
Analysis
Code: 13:11:15 UTC,
c,
verify,
result: Passed
// you can write to stdout for debugging purposes, e.g.
int solution(int A[], int N) {
// write your code in C99
// printf("this is a debug message\n");
long long count =0;
int B[N];
B[0] = A[0];
for(long i =1; i<N;i++)
{
B[i]=A[i];
A[i] += A[i-1];
}
long last = A[N-1];
for(long i =0; i<N;i++)
{
if (B[i]==0)
{
count += last-A[i];
}
}
return count;
}
User test case 1:
[0, 0, 1, 1, 0, 0, 1]
Analysis
Code: 13:11:18 UTC,
c,
final,
score:
66
// you can write to stdout for debugging purposes, e.g.
int solution(int A[], int N) {
// write your code in C99
// printf("this is a debug message\n");
long long count =0;
int B[N];
B[0] = A[0];
for(long i =1; i<N;i++)
{
B[i]=A[i];
A[i] += A[i-1];
}
long last = A[N-1];
for(long i =0; i<N;i++)
{
if (B[i]==0)
{
count += last-A[i];
}
}
return count;
}Analysis summary
The following issues have been detected: wrong answers.
Analysis
expand all
Correctness tests
1.
0.007 s
OK
2.
0.007 s
OK
1.
0.007 s
OK
2.
0.007 s
OK
3.
0.006 s
OK
4.
0.006 s
OK
1.
0.006 s
OK
1.
0.006 s
OK
expand all
Performance tests
1.
0.007 s
OK
1.
0.012 s
WRONG ANSWER,
got 1248768710 expected -1
1.
0.012 s
WRONG ANSWER,
got -1794967296 expected -1
2.
0.010 s
OK
1.
0.012 s
WRONG ANSWER,
got 1250025000 expected -1
2.
0.011 s
OK
1.
0.012 s
OK
2.
0.012 s
OK
3.
0.012 s
OK