SodhanaLibrary

function canCompleteCircuit(gas, cost) {
    var sumRemaining = 0; // track current remaining
    var total = 0; // track total remaining
    var start = 0; 
 
    for (var i = 0; i < gas.length; i++) {
        var remaining = gas[i] - cost[i];
 
        //if sum remaining of (i-1) >= 0, continue 
        if (sumRemaining >= 0) { 
            sumRemaining += remaining;
        //otherwise, reset start index to be current
        } else {
            sumRemaining = remaining;
            start = i;
        }
        total += remaining;
    }
 
    if (total >= 0){
        return start;
    }else{
        return -1;
    }
}
console.log(canCompleteCircuit([1,2,3,4,5],[1,3,2,4,5]));