PassingCars.js

// Solution 1:
function solution(A) {
    // write your code in JavaScript (Node.js 8.9.4)
    let wests=[];
    wests[A.length-1] = A[A.length-1]==1 ? 1 : 0;
    for(let i=A.length-2; i>-1; i--)
    {
        wests[i] = wests[i+1];
        if(A[i]==1)
            wests[i]++;
    }
    
    let sum=0;
    for(let cntr=0; cntr< A.length; cntr++){
        let east = A[cntr];
        if(east != 0)
            continue;
        sum += wests[cntr];
        if(sum > 1000000000)
            return -1
    }

     return sum;
}

// Solution 2:
// Solution 1:
function solution(A) {
    // write your code in JavaScript (Node.js 8.9.4)
    let sum = 0;
    let ones = 0;
    for(let i=A.length-1; i>-1; i--)
    {
        if(A[i] == 0)
            sum += ones;
        else
            ones++;
            
        if(sum > 1000000000 )
            return -1;
    }

     return sum;
}