寻找比目标字母大的最小字母
题目:
给你一个排序后的字符列表 letters ，列表中只包含小写英文字母。另给出一个目标字母 target，请你寻找在这一有序列表里比目标字母大的最小字母。
在比较时，字母是依序循环出现的。举个例子：
如果目标字母 target = 'z' 并且字符列表为 letters = ['a', 'b']，则答案返回 'a'
示例：
输入:
letters = ["c", "f", "j"]
target = "a"
输出: "c"
输入:
letters = ["c", "f", "j"]
target = "c"
输出: "f"
输入:
letters = ["c", "f", "j"]
target = "d"
输出: "f"
输入:
letters = ["c", "f", "j"]
target = "g"
输出: "j"
输入:
letters = ["c", "f", "j"]
target = "j"
输出: "c"
输入:
letters = ["c", "f", "j"]
target = "k"
输出: "c
解题思路: 一道搜索左边界的二分题目, 套用模板答题即可
class Solution {
public char nextGreatestLetter(char[] letters, char target) {
int l = 0, r = letters.length - 1;
while(l <= r) {
int mid = l + (r - l) / 2;
char ch = letters[mid];
if(ch < target) {
l = mid + 1;
} else if(ch == target) {
l = mid + 1;
} else {
r = mid - 1;
}
}
return l == letters.length ? letters[0] : letters[l];
}
}