Problem
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Given an input string, reverse the string word by word. A word is defined as a sequence of non-space characters.The input string does not contain leading or trailing spaces and the words are always separated by a single space.
For example,
Given s = "the sky is blue",
return "blue is sky the".Could you do it in-place without allocating extra space?
Solution
先reverse string，之后reverse每一个word。
class Solution {
public:
void reverseStr(string &s, int i, int j) {
while (i < j) {
char c = s[i];
s[i] = s[j];
s[j] = c;
i++;
j--;
}
}
void reverseWords(string &s) {
if (s.size() == 0) {
return;
}
reverseStr(s, 0, s.size() - 1);
int start = 0;
int end;
for(int i = 0; i < s.size(); i++) {
if (s[i] == ' ') {
end = i - 1;
reverseStr(s, start, end);
start = i + 1;
}
}
if (s[s.size() - 1] != ' ') {
reverseStr(s, start, s.size() - 1);
}
}
};
