LeetCode Q151: Reverse Words in a String

Given an input string, reverse the string word by word.

For example,
Given s = "the sky is blue",
return "blue is sky the".

Update (2015-02-12):
For C programmers: Try to solve it in-place in O(1) space.

	class Solution {
	public:
	void reverseWords(string &s) {
	if(s.length()==0)
	return;
	int p0=0; while(s[p0]==' '){p0++;}
	int p1=s.length()-1; while(s[p1]==' '){p1--;}
	if(p0<=p1)
	s=s.substr(p0, p1-p0+1);
	else{
	s=s.substr(0, 0);
	return;
	}
	p0=0;
	p1=s.length()-1;
	while(p0<p1){
	char tmp=s[p0];
	s[p0]=s[p1];
	s[p1]=tmp;
	p0++;
	p1--;
	}
	p0=0; p1=0;
	while(p1<=s.length()-1){
	if(s[p1]!=' '){
	s[p0]=s[p1];
	p0++;
	p1++;
	continue;
	}
	s[p0]=s[p1];
	p0++;
	while(s[p1]==' '&&p1<=s.length()-1){p1++;}
	}
	s=s.substr(0, p0);
	p0=0; p1=0;
	while(p0<=s.length()-1){
	p1=p0;
	while(s[p1]!=' '&&p1<=s.length()-1){p1++;}
	int nextp=p1;
	p1--;
	while(p0<p1){
	char tmp=s[p0];
	s[p0]=s[p1];
	s[p1]=tmp;
	p0++;
	p1--;
	}
	p0=nextp+1;
	}
	}
	};

view raw Q151ReverseWordsinString.cpp hosted with ❤ by GitHub

Round 2 solution:

	class Solution {
	public:
	void reverseWords(string &s) {
	if(s.empty())
	return;
	int p0=0, p1=p0;
	string tmps;
	while(p0<s.length()){
	if(!isspace(s[p0])&&(p0==0 || isspace(s[p0-1]))){
	p1 = p0;
	while(s[p1]!=' '&&p1!=s.length()) p1++;
	int tmp = p1--;
	string ss = s.substr(p0, p1-p0+1);
	int p00=0, p11=ss.length()-1;
	while(p00<p11) swap(ss[p00++], ss[p11--]);
	tmps = tmps.empty()? ss: tmps+string(" ")+ss;
	p0 = tmp;
	}
	p0++;
	}
	s=tmps;
	reverse(s.begin(), s.end());
	}
	};

view raw Q151Rnd2.cpp hosted with ❤ by GitHub