40 lines
1.4 KiB
C++
40 lines
1.4 KiB
C++
// Source : https://oj.leetcode.com/problems/gas-station/
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// Author : Hao Chen
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// Date : 2014-10-11
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/**********************************************************************************
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*
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* There are N gas stations along a circular route, where the amount of gas at station i is gas[i].
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*
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* You have a car with an unlimited gas tank and it costs cost[i] of gas to travel from station i to
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* its next station (i+1). You begin the journey with an empty tank at one of the gas stations.
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*
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* Return the starting gas station's index if you can travel around the circuit once, otherwise return -1.
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*
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* Note:
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* The solution is guaranteed to be unique.
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*
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*
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**********************************************************************************/
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class Solution {
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public:
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int canCompleteCircuit(vector<int> &gas, vector<int> &cost) {
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int current = 0;
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int start = gas.size(); //start from the end to beginning
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int total = 0;
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do {
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if (total + gas[current] - cost[current] >= 0) {
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total += (gas[current] - cost[current]);
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current++; // can go from current to current+1
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}else{
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start--; //not enough gas, try to start the one before origin start point.
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total += (gas[start] - cost[start]);
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}
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} while(current != start);
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return total>=0 ? start % gas.size() : -1;
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}
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};
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