LeetCode Link: https://leetcode.com/problems/reverse-words-in-a-string/
Language: C#
Problem Statement
Given an input string s, reverse the order of the words.
A word is defined as a sequence of non-space characters.
The words in s will be separated by at least one space.
Return a string of the words in reverse order concatenated by a single space.
Note that s may contain leading or trailing spaces or multiple spaces between two words.
The returned string should only have a single space separating the words.
Do not include any extra spaces.
Example 1:
Input: s = "the sky is blue"
Output: "blue is sky the"
Example 2:
Input: s = " hello world "
Output: "world hello"
Explanation: Your reversed string should not contain leading or trailing spaces.
Example 3:
Input: s = "a good example"
Output: "example good a"
Explanation: You need to reduce multiple spaces between two words to a single space in the reversed string.
Example 4:
Input: s = " Bob Loves Alice "
Output: "Alice Loves Bob"
Example 5:
Input: s = "Alice does not even like bob"
Output: "bob like even not does Alice"
Constraints
- 1 <= s.length <= 104
- s contains English letters (upper-case and lower-case), digits, and spaces ‘ ‘.
- There is at least one word in s.
Solution
public class Solution
{
public string ReverseWords(string s)
{
int start = 0;
int pos = s.Length - 1;
while (s[start] == ' ')
start++;
while (s[pos] == ' ')
pos--;
int len = 0;
var sb = new StringBuilder(s.Length);
while (pos >= start)
{
len = 0;
while(pos>=start && s[pos] != ' ')
{
pos--;
len++;
}
if (len > 0)
{
for (int i=0; i<=len; i++)
{
if(pos+i>=start && s[pos+i] != ' ')
{
sb.Append(s[pos+i]);
}
}
sb.Append(' ');
}
pos--;
}
sb.Remove(sb.Length-1, 1);
return sb.ToString();
}
}
Complexity
Time Complexity: O(n)
Space Complexity: O(1)