134. Gas Station

Author: NilStack

README.md

@@ -2,11 +2,12 @@
 
 Not only Leetcode solutions in Swift.
 
-* [1.Two Sum](https://leetcode.com/problems/two-sum/)
+* [1. Two Sum](https://leetcode.com/problems/two-sum/)
 * [15. 3Sum](https://leetcode.com/problems/3sum/)
 * [16. 3Sum Closest](https://leetcode.com/problems/3sum-closest/)
 * [18. 4Sum](https://leetcode.com/problems/4sum/)
 * [46. Group Anagrams](https://leetcode.com/problems/anagrams/)
+* [134. Gas Station](https://leetcode.com/problems/gas-station/)
 * [167. Two Sum II - Input array is sorted](https://leetcode.com/problems/two-sum-ii-input-array-is-sorted/)
 * [170. Two Sum III - Data structure design](https://leetcode.com/problems/two-sum-iii-data-structure-design)
 * [Two Sum - Less than or equal to target](http://www.lintcode.com/en/problem/two-sum-less-than-or-equal-to-target/)

SwiftyLeetCode.playground/Contents.swift

@@ -227,6 +227,36 @@ extension Solution {
 let groupAnagramsStrs = ["eat", "tea", "tan", "ate", "nat", "bat"]
 Solution.groupAnagrams(strs: groupAnagramsStrs)
 
+/**
+ * 134. Gas Station
+ * https://leetcode.com/problems/gas-station/
+ */
+
+extension Solution {
+    class func canCompleteCircuit(gas: [Int]?, cost: [Int]?) -> Int {
+        
+        guard let gas = gas, let cost = cost, gas.count > 0, cost.count > 0 else {
+            return -1
+        }
+        
+        var sum = 0
+        var total = 0
+        var index = -1
+        
+        for i in 0..<gas.count {
+            sum += gas[i] - cost[i]
+            total += gas[i] - cost[i]
+            
+            if (sum < 0) {
+                index = i
+                sum = 0
+            }
+        }
+        
+        return total < 0 ? -1 : index + 1
+    }
+}
+
 /**
  * 167. Two Sum II - Input array is sorted
  * https://leetcode.com/problems/two-sum-ii-input-array-is-sorted/