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:
function solution(A);
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.
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
let east = 0
let passing = 0
for (let i of A) {
if (i === 0) {
east += 1
} else {
passing += east
}
}
if (passing > 100000 || passing === 0) {
return -1
}
return passing
}
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
let east = 0
let passing = 0
for (let i of A) {
if (i === 0) {
east += 1
} else {
passing += east
}
}
if (passing > 1000000000 || passing === 0) {
return -1
}
return passing
}
[0]
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
let east = 0
let passing = 0
for (let i of A) {
if (i === 0) {
east += 1
} else {
passing += east
}
}
if (passing > 1000000000 || passing < 0) {
return -1
}
return passing
}
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
let east = 0
let passing = 0
for (let i of A) {
if (i === 0) {
east += 1
} else {
passing += east
}
}
if (passing > 1000000000) {
return -1
}
return passing
}
[0]
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
let east = 0
let passing = 0
for (let i of A) {
if (i === 0) {
east += 1
} else {
passing += east
}
}
if (passing > 1000000000) {
return -1
}
return passing
}
[0]
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
let east = 0
let passing = 0
for (let i of A) {
if (i === 0) {
east += 1
} else {
passing += east
}
}
if (passing > 1000000000) {
return -1
}
return passing
}
The solution obtained perfect score.