https://oj.leetcode.com/problems/reverse-words-in-a-string/

Reverse Words in a String

class Solution {
public:
	void reverseWords(string &s) {
		int N = s.size();
		string ans(N + 1, '\0');

		int state = 0;
		bool first_word = true;
		int j = 0;
		for (int i = N - 1; i >= 0; --i) {
			if (state == 0 && s[i] != ' ')
				state = 1;
			if (state == 1) {
				if (s[i] != ' ' && i != 0)
					continue;

				if (first_word)
					first_word = false;
				else
					ans[j++] = ' ';

				int sidx;
				if (s[i] == ' ')
					sidx = i + 1;
				else if (i == 0)
					sidx = 0;

				j = proc(ans, j, s, sidx);
				state = 0;
			}
		}
		ans[j] = '\0';
		s = ans.c_str();
	}
	int proc(string &ans, int j, const string &src, int i) {
		for (; i<src.size() && src[i] != ' '; ++i)
			ans[j++] = src[i];

		return j;
	}
};