134. 加油站

Author: w2xi

README.md

@@ -83,6 +83,7 @@
 |125|[验证回文串](https://leetcode.cn/problems/valid-palindrome/)|[JavaScript](./algorithms/valid-palindrome.js)|Easy|
 |129|[求根节点到叶节点数字之和](https://leetcode.cn/problems/sum-root-to-leaf-numbers/)|[JavaScript](./algorithms/sum-root-to-leaf-numbers.js)|Medium|
 |131|[分割回文串](https://leetcode.cn/problems/palindrome-partitioning/)|[JavaScript](./algorithms/palindrome-partitioning.js)|Medium|
+|134|[加油站](https://leetcode.cn/problems/gas-station/)|[JavaScript](./algorithms/gas-station.js)|Medium|
 |136|[只出现一次的数字](https://leetcode-cn.com/problems/single-number/)|[JavaScript](./algorithms/single-number.js)|Easy|
 |141|[环形链表](https://leetcode-cn.com/problems/linked-list-cycle/)|[JavaScript](./algorithms/linked-list-cycle.js)|Easy|
 |142|[环形链表 II](https://leetcode.cn/problems/linked-list-cycle-ii/)|[JavaScript](./algorithms/linked-list-cycle-ii.js)|Medium|

algorithms/gas-station.js

@@ -0,0 +1,45 @@
+/**
+ * 134. 加油站
+ * @param {number[]} gas
+ * @param {number[]} cost
+ * @return {number}
+ */
+var canCompleteCircuit = function (gas, cost) {
+  // 暴力方法
+
+  for (let i = 0; i < gas.length; i++) {
+    let restGas = gas[i] - cost[i]; // 记录剩余油量
+    let index = (i + 1) % gas.length;
+
+    while (restGas > 0 && index !== i) {
+      // 模拟以 i 为起点行驶一周
+      restGas += gas[index] - cost[index];
+      index = (index + 1) % gas.length;
+    }
+    // 如果以 i 为起点跑一圈, 剩余油量 >= 0, 返回该起始位置
+    if (restGas >= 0 && index === i) {
+      return i;
+    }
+  }
+
+  return -1;
+};
+
+// 贪心方法
+var canCompleteCircuit2 = function (gas, cost) {
+  let start = 0;
+  let totalSum = 0;
+  let currSum = 0;
+
+  for (let i = 0; i < gas.length; i++) {
+    currSum += gas[i] - cost[i];
+    totalSum += gas[i] - cost[i];
+
+    if (currSum < 0) {
+      start = i + 1;
+      currSum = 0;
+    }
+  }
+
+  return totalSum < 0 ? -1 : start;
+};