> For the complete documentation index, see [llms.txt](https://dfine.gitbook.io/leetcode/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://dfine.gitbook.io/leetcode/680.valid_palindrome_ii.md).

# 680.Valid Palindrome II

**680.Valid Palindrome II**

难度:Easy Given a non-empty string s, you may delete at most one character. Judge whether you can make it a palindrome.

```
Example 1:
Input: "aba"
Output: True
Example 2:
Input: "abca"
Output: True
Explanation: You could delete the character 'c'.
Note:
The string will only contain lowercase characters a-z. The maximum length of the string is 50000.
```

从头尾开始往内遍历，如果直接遍历完是回文返回true，如果遇到不相等的，将左、右分别删掉一个然后分别检查是否是回文字串，如果是返回true，否则返回 false。\
时间复杂度O(n)

```
class Solution {
bool isValid(int left,int right,string s)
{
    while(left<right)
    {
        if(s[left++] != s[right--]) 
            return false;
    }
    return true;
}
public:
    bool validPalindrome(string s) {
        if(s.length()<3) return true;
        int left=0;
        int right=s.length()-1;
        while(left<right)
        {
            if(s[left]!=s[right]) return isValid(left+1,right,s) || isValid(left,right-1,s);
            left++;
            right--;
     
        }
        return true;
    }
};
```

> 执行用时 :84 ms, 在所有 C++ 提交中击败了95.29%的用户\
> 内存消耗 :26.1 MB, 在所有 C++ 提交中击败了53.76%的用户


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