leetcode 345. Reverse Vowels of a String 只反转字符串元音字符

青旅半醒 2022-06-07 01:16 141阅读 0赞

Write a function that takes a string as input and reverse only the vowels of a string.

Example 1:  
Given s = “hello”, return “holle”.

Example 2:  
Given s = “leetcode”, return “leotcede”.

Note:  
The vowels does not include the letter “y”.

这道题考察的是反转一个字符串中的所有的元音字符，使用双指针，然后交换即可。

代码如下:

/*
     * 双向指针，一次遍历即可，交换所有的元音字符
     * */
    class Solution 
    {
         public String reverseVowels(String s) 
            {
                StringBuilder builder=new StringBuilder(s);
    
                int i=0;
                int j=builder.length()-1;
                while(i<j)
                {
                    boolean a=isVowel(builder.charAt(i));
                    boolean b=isVowel(builder.charAt(j));
                    if(a&&b)
                    {
                        char tmp=builder.charAt(i);
                        builder.setCharAt(i, builder.charAt(j));
                        builder.setCharAt(j, tmp);
                        i++;
                        j--;
                    }else if(a && !b)
                        j--;
                    else if(!a && b)
                        i++;
                    else 
                    {
                        i++;
                        j--;
                    }
                }
                return builder.toString();
        }
    
        public boolean isVowel(char a) 
        {
            if(a=='a'||a=='e'||a=='i'||a=='o'||a=='u'
             ||a=='A'||a=='E'||a=='I'||a=='O'||a=='U')
                return true;
            else
                return false;
        }
    
    }

下面是C++的做法，遍历即可

代码如下：

#include <iostream>
    #include <vector>
    #include <map>
    #include <unordered_map>
    #include <set>
    #include <unordered_set>
    #include <queue>
    #include <stack>
    #include <string>
    #include <climits>
    #include <algorithm>
    #include <sstream>
    #include <functional>
    #include <bitset>
    #include <numeric>
    #include <cmath>
    #include <regex>
    
    using namespace std;
    
    
    
    class Solution 
    {
    public:
        string reverseVowels(string s) 
        {
            if (s.length() <= 0)
                return s;
    
            int i = 0, j = s.length() - 1;
            while (i < j)
            {
                bool a = isVowels(s[i]);
                bool b = isVowels(s[j]);
                if (a == true && b == true)
                {
                    swap(s[i], s[j]);
                    i++;
                    j--;
                }else if (a == true && b == false)
                    j--;
                else if (a == false && b == true)
                    i++;
                else
                {
                    i++;
                    j--;
                }
    
            }
            return s;
        }
    
        bool isVowels(char a)
        {
            if (a == 'a' || a == 'e' || a == 'i' || a == 'o' || a == 'u'|| a == 'A' || a == 'E' || a == 'I' || a == 'O' || a == 'U')
                return true;
            else
                return false;
        }
    };