leetcode:(69)Find Smallest Letter Greater Than Target(java)

最新推荐文章于 2019-04-19 15:28:29 发布

原创最新推荐文章于 2019-04-19 15:28:29 发布 · 377 阅读

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本文介绍了一种使用二分查找算法解决寻找比目标字母大的最小字母的问题的方法。通过具体的例子展示了如何在已排序的字符列表中找到目标字母之后的下一个字母，包括当目标字母位于列表末尾时的特殊情况处理。

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题目：

Given a list of sorted characters letters containing only lowercase letters, and given a target letter target, find the smallest element in the list that is larger than the given target.

Letters also wrap around. For example, if the target is target = 'z' and letters = ['a', 'b'], the answer is 'a'.

Examples:

Input:
letters = ["c", "f", "j"]
target = "a"
Output: "c"

Input:
letters = ["c", "f", "j"]
target = "c"
Output: "f"

Input:
letters = ["c", "f", "j"]
target = "d"
Output: "f"

Input:
letters = ["c", "f", "j"]
target = "g"
Output: "j"

Input:
letters = ["c", "f", "j"]
target = "j"
Output: "c"

Input:
letters = ["c", "f", "j"]
target = "k"
Output: "c"

解题思路：

利用二分查找。具体思路及代码如下：

package Leetcode_Github;

public class BinarySearch_NextGreaterLetters_744_1113 {
    public char NextGreaterLetter(char[] letters, char target) {
        int l = 0;
        int h = letters.length - 1;
        while (l <= h) {
            int mid = l + (h - l) / 2;
            if (letters[mid] > target) {
                h = mid - 1;
            } else
                l = mid + 1;
        }
        return l < letters.length ? letters[l] : letters[0];
    }
}