1+ // Source : https://leetcode.com/problems/reverse-words-in-a-string/
2+ // Author : henrytien
3+ // Date : 2022年02月09日
4+ 5+ /* ****************************************************************************************************
6+ *
7+ * Given an input string s, reverse the order of the words.
8+ *
9+ * A word is defined as a sequence of non-space characters. The words in s will be separated by at
10+ * least one space.
11+ *
12+ * Return a string of the words in reverse order concatenated by a single space.
13+ *
14+ * Note that s may contain leading or trailing spaces or multiple spaces between two words. The
15+ * returned string should only have a single space separating the words. Do not include any extra
16+ * spaces.
17+ *
18+ * Example 1:
19+ *
20+ * Input: s = "the sky is blue"
21+ * Output: "blue is sky the"
22+ *
23+ * Example 2:
24+ *
25+ * Input: s = " hello world "
26+ * Output: "world hello"
27+ * Explanation: Your reversed string should not contain leading or trailing spaces.
28+ *
29+ * Example 3:
30+ *
31+ * Input: s = "a good example"
32+ * Output: "example good a"
33+ * Explanation: You need to reduce multiple spaces between two words to a single space in the reversed
34+ * string.
35+ *
36+ * Constraints:
37+ *
38+ * 1 <= s.length <= 104
39+ * s contains English letters (upper-case and lower-case), digits, and spaces ' '.
40+ * There is at least one word in s.
41+ *
42+ * Follow-up: If the string data type is mutable in your language, can you solve it in-place with O(1)
43+ * extra space?
44+ ******************************************************************************************************/
45+ 46+ #include " ../inc/ac.h"
47+ class Solution
48+ {
49+ public:
50+ string reverseWords (string s)
51+ {
52+ 53+ reverse (s.begin (), s.end ());
54+ int n = s.size ();
55+ int index = 0 ;
56+ for (int start = 0 ; start < n; start++)
57+ {
58+ if (s[start] != ' '
59+ {
60+ // Go to begining of the word
61+ if (index != 0 )
62+ s[index++] = ' '
63+ 64+ int end = start;
65+ // Go to the end of the word
66+ while (end < n && s[end] != ' '
67+ {
68+ s[index++] = s[end++];
69+ }
70+ 71+ // Reverse the word
72+ reverse (s.begin () + index - (end - start), s.begin () + index);
73+ 74+ // Move to the next word
75+ start = end;
76+ }
77+ }
78+ 79+ s.erase (s.begin () + index, s.end ());
80+ return s;
81+ }
82+ };
83+ 84+ int main ()
85+ {
86+ 87+ string s = " the sky is blue"
88+ cout << Solution ().reverseWords (s) << " \n "
89+ return 0 ;
90+ }
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