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134.gas-station.go
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134.gas-station.go
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/*
* @lc app=leetcode id=134 lang=golang
*
* [134] Gas Station
*
* https://leetcode.com/problems/gas-station/description/
*
* algorithms
* Medium (40.91%)
* Likes: 2642
* Dislikes: 419
* Total Accepted: 266.4K
* Total Submissions: 649.5K
* Testcase Example: '[1,2,3,4,5]\n[3,4,5,1,2]'
*
* There are n gas stations along a circular route, where the amount of gas at
* the i^th station is gas[i].
*
* You have a car with an unlimited gas tank and it costs cost[i] of gas to
* travel from the i^th station to its next (i + 1)^th station. You begin the
* journey with an empty tank at one of the gas stations.
*
* Given two integer arrays gas and cost, return the starting gas station's
* index if you can travel around the circuit once in the clockwise direction,
* otherwise return -1. If there exists a solution, it is guaranteed to be
* unique
*
*
* Example 1:
*
*
* Input: gas = [1,2,3,4,5], cost = [3,4,5,1,2]
* Output: 3
* Explanation:
* Start at station 3 (index 3) and fill up with 4 unit of gas. Your tank = 0 +
* 4 = 4
* Travel to station 4. Your tank = 4 - 1 + 5 = 8
* Travel to station 0. Your tank = 8 - 2 + 1 = 7
* Travel to station 1. Your tank = 7 - 3 + 2 = 6
* Travel to station 2. Your tank = 6 - 4 + 3 = 5
* Travel to station 3. The cost is 5. Your gas is just enough to travel back
* to station 3.
* Therefore, return 3 as the starting index.
*
*
* Example 2:
*
*
* Input: gas = [2,3,4], cost = [3,4,3]
* Output: -1
* Explanation:
* You can't start at station 0 or 1, as there is not enough gas to travel to
* the next station.
* Let's start at station 2 and fill up with 4 unit of gas. Your tank = 0 + 4 =
* 4
* Travel to station 0. Your tank = 4 - 3 + 2 = 3
* Travel to station 1. Your tank = 3 - 3 + 3 = 3
* You cannot travel back to station 2, as it requires 4 unit of gas but you
* only have 3.
* Therefore, you can't travel around the circuit once no matter where you
* start.
*
*
*
* Constraints:
*
*
* gas.length == n
* cost.length == n
* 1 <= n <= 10^4
* 0 <= gas[i], cost[i] <= 10^4
*
*
*/
package leetgo
// @lc code=start
func canCompleteCircuit(gas []int, cost []int) int {
start, n := 0, len(gas)
for start < n {
j, left := 0, 0
for j < n {
index := (start + j) % n
left += gas[index] - cost[index]
if left < 0 {
break
}
j++
}
if j == n {
return start
}
start += j + 1
}
return -1
}
// @lc code=end