134

class Solution {
public:
    int canCompleteCircuit(vector<int>& gas, vector<int>& cost) {
        int n=gas.size(), total=0, start=0, curr=0;
        for(int i=0; i<n; i++){
            total += gas[i]-cost[i];
            curr += gas[i]-cost[i];
            if(curr< 0){
                start=i+1;
                curr=0;
            }
        }
        return total>=0 ? start:-1;
    }
};