{ "data": { "question": { "questionId": "1627", "questionFrontendId": "1503", "categoryTitle": "Algorithms", "boundTopicId": 314888, "title": "Last Moment Before All Ants Fall Out of a Plank", "titleSlug": "last-moment-before-all-ants-fall-out-of-a-plank", "content": "

We have a wooden plank of the length n units. Some ants are walking on the plank, each ant moves with a speed of 1 unit per second. Some of the ants move to the left, the other move to the right.

\n\n

When two ants moving in two different directions meet at some point, they change their directions and continue moving again. Assume changing directions does not take any additional time.

\n\n

When an ant reaches one end of the plank at a time t, it falls out of the plank immediately.

\n\n

Given an integer n and two integer arrays left and right, the positions of the ants moving to the left and the right, return the moment when the last ant(s) fall out of the plank.

\n\n

 

\n

Example 1:

\n\"\"\n
\nInput: n = 4, left = [4,3], right = [0,1]\nOutput: 4\nExplanation: In the image above:\n-The ant at index 0 is named A and going to the right.\n-The ant at index 1 is named B and going to the right.\n-The ant at index 3 is named C and going to the left.\n-The ant at index 4 is named D and going to the left.\nThe last moment when an ant was on the plank is t = 4 seconds. After that, it falls immediately out of the plank. (i.e., We can say that at t = 4.0000000001, there are no ants on the plank).\n
\n\n

Example 2:

\n\"\"\n
\nInput: n = 7, left = [], right = [0,1,2,3,4,5,6,7]\nOutput: 7\nExplanation: All ants are going to the right, the ant at index 0 needs 7 seconds to fall.\n
\n\n

Example 3:

\n\"\"\n
\nInput: n = 7, left = [0,1,2,3,4,5,6,7], right = []\nOutput: 7\nExplanation: All ants are going to the left, the ant at index 7 needs 7 seconds to fall.\n
\n\n

 

\n

Constraints:

\n\n\n", "translatedTitle": "所有蚂蚁掉下来前的最后一刻", "translatedContent": "

有一块木板，长度为 n 个 单位 。一些蚂蚁在木板上移动，每只蚂蚁都以 每秒一个单位 的速度移动。其中，一部分蚂蚁向 左 移动，其他蚂蚁向 右 移动。

\n\n

当两只向 不同 方向移动的蚂蚁在某个点相遇时，它们会同时改变移动方向并继续移动。假设更改方向不会花费任何额外时间。

\n\n

而当蚂蚁在某一时刻 t 到达木板的一端时，它立即从木板上掉下来。

\n\n

给你一个整数 n 和两个整数数组 left 以及 right 。两个数组分别标识向左或者向右移动的蚂蚁在 t = 0 时的位置。请你返回最后一只蚂蚁从木板上掉下来的时刻。

\n\n

 

\n\n

示例 1：

\n\n

 

\n\n

\"\"

\n\n
\n输入：n = 4, left = [4,3], right = [0,1]\n输出：4\n解释：如上图所示：\n-下标 0 处的蚂蚁命名为 A 并向右移动。\n-下标 1 处的蚂蚁命名为 B 并向右移动。\n-下标 3 处的蚂蚁命名为 C 并向左移动。\n-下标 4 处的蚂蚁命名为 D 并向左移动。\n请注意，蚂蚁在木板上的最后时刻是 t = 4 秒，之后蚂蚁立即从木板上掉下来。（也就是说在 t = 4.0000000001 时，木板上没有蚂蚁）。
\n\n

示例 2：

\n\n

\"\"

\n\n
\n输入：n = 7, left = [], right = [0,1,2,3,4,5,6,7]\n输出：7\n解释：所有蚂蚁都向右移动，下标为 0 的蚂蚁需要 7 秒才能从木板上掉落。\n
\n\n

示例 3：

\n\n

\"\"

\n\n
\n输入：n = 7, left = [0,1,2,3,4,5,6,7], right = []\n输出：7\n解释：所有蚂蚁都向左移动，下标为 7 的蚂蚁需要 7 秒才能从木板上掉落。\n
\n\n

 

\n\n

提示：

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