[LeetCode]186. Flip word II in string

subject

 Title Description 
 Given a string , Flip each word in the string one by one .

 Example ：
   Input : ["t","h","e"," ","s","k","y"," ","i","s"," ","b","l","u","e"]
   Output : ["b","l","u","e"," ","i","s"," ","s","k","y"," ","t","h","e"]

 Be careful ：
   A word is defined as a series of characters that do not contain spaces 
   The input string will not contain leading or trailing spaces 
   Words are always separated from each other by a single space 

 Advanced ：
   Use  O(1)  In situ solution of extra space complexity 



 author ： Jun Wang is not in his early days 
 link ：https://www.jianshu.com/p/9d624882d786
 source ： Simple books 
 The copyright belongs to the author . Commercial reprint please contact the author for authorization , Non-commercial reprint please indicate the source .

Method 1： Flip

public void reverseWords(char[] str) {
    
    int i = 0;
    for (int j = 0; j < str.length; j++) {
    
        if (str[j] == ' ') {
    
            reverse(str, i, j);
            i = j + 1;
        }
    }
    reverse(str, i, str.length);
    System.out.println(String.valueOf(str));
    reverse(str, 0, str.length);
}

/** *  take  ch  Of  [l, r]  Flip , *  Be careful ,[l,r)  It's left and right  * * @param ch * @param l * @param r */
private void reverse(char[] ch, int l, int r) {
    
    for (int k = l; k < (l + r) / 2; k++) {
    
        char tmp = ch[k];  //  Location  k  The elements of 
        int g = r - 1 - k + l;  //  Location  k  The symmetrical position of 
        ch[k] = ch[g];
        ch[g] = tmp;
    }
}