Leetcode (WU): Gas station

There was N gas stations along a circular route, where the amount of gas at Station I was gas[i] .

You had a car with an unlimited gas tank and it costs of gas to travel from station cost[i] I to its next station (i+ 1). You begin the journey with a empty tank at one of the gas stations.

Return The starting gas station's index If you can travel around the circuit once, otherwise return-1.

Note:

The solution is guaranteed to be unique.

Class Solution {public:    int. cancompletecircuit (vector<int>& gas, vector<int>& cost) {        int Length=gas.size ();    Vector<int> Tmpgas (length,0);        for (int i=0;i<length;++i)    {    tmpgas[i]=gas[i]-cost[i];//a new array of difference, representing the complement or consumption    }        int startindex=0 ;//initial starting point    int sum=tmpgas[startindex];        int i=0;    while (true)    {    i++;    if (i>=length)    {    i=i-length;    }        if (sum<0)    {    startindex=i;//one of the following nodes as the starting point    if (startindex==0)    return-1;//back to the initial starting point, the loop    begins to appear Sum=tmpgas[startindex];    }    else    {    sum+=tmpgas[i];

<span style= "White-space:pre" ></span>    //has reached the finish line to determine if the whole process can be successfully completed    if (startindex==0 && i== Length-1)    {//If the starting point is 0, the current node is also the last nodes    if (sum<0)    return-1;    else    return startIndex;    }        if (i==startindex-1)    {//If the current node is the last node of the loop if    (sum>=0)    return startIndex;    else return-1;}}}}    ;

Leetcode (WU): Gas station