744.Find Smallest Letter Greater Than Target
744. Find Smallest Letter Greater Than Target
难度:Easy
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'.
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Examples:
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Input:
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letters = ["c", "f", "j"]
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target = "a"
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Output: "c"
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Input:
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letters = ["c", "f", "j"]
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target = "c"
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Output: "f"
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Input:
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letters = ["c", "f", "j"]
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target = "d"
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Output: "f"
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Input:
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letters = ["c", "f", "j"]
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target = "g"
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Output: "j"
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Input:
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letters = ["c", "f", "j"]
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target = "j"
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Output: "c"
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Input:
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letters = ["c", "f", "j"]
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target = "k"
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Output: "c"
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Note:
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letters has a length in range [2, 10000].
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letters consists of lowercase letters, and contains at least 2 unique letters.
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target is a lowercase letter.
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直接找出當target大於給定目標值時的最小值,如果沒有,返回整個數組的最小值。 第一種方法:遞歸
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class Solution {
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public:
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char nextGreatestLetter(vector<char>& letters, char target) {
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char res='z'+1;
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for(auto c:letters)
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if(c>target )
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res=min(res,c);
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return res=='z'+1?nextGreatestLetter(letters, target-26): res ;
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}
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};
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执行用时 :24 ms, 在所有 C++ 提交中击败了22.61%的用户 内存消耗 :9 MB, 在所有 C++ 提交中击败了84.87%的用户
第二種方法,直接用一個變量保存最小值。
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class Solution {
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public:
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char nextGreatestLetter(vector<char>& letters, char target) {
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char res='z'+1;
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char minC=res;
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for(auto c:letters)
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{
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if(c>target )
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res=min(res,c);
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minC=min(minC,c);
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}
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return res=='z'+1?minC: res ;
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}
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};
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执行用时 :16 ms, 在所有 C++ 提交中击败了77.00%的用户 内存消耗 :9 MB, 在所有 C++ 提交中击败了88.11%的用户
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