C++中反转字符串单词字符顺序的两种方法

输入:  "Hello World"
输出:  "olleH dlroW"

Hello → olleH
World → dlroW

#include <iostream>
#include <sstream>
#include <algorithm>
using namespace std;
string reverseWords(string s) {
    stringstream ss(s);
    string word;
    string result;
    while (ss >> word) {
        reverse(word.begin(), word.end());
        result += word + " ";
    }
    result.pop_back();
    return result;
}
int main() {
    string str = "Hello World";
    cout << reverseWords(str) << endl;
    return 0;
}

olleH dlroW

O(n)

O(n)

#include <iostream>
#include <algorithm>

using namespace std;

string reverseWords(string s) {

    int start = 0;

    for (int i = 0; i <= s.size(); i++) {

        if (i == s.size() || s[i] == ' ') {

            reverse(s.begin() + start, s.begin() + i);

            start = i + 1;
        }
    }

    return s;
}

int main() {

    string str = "Hello World";

    cout << reverseWords(str) << endl;

    return 0;
}

olleH dlroW

O(n)

O(1)

"Hello World"
→ "World Hello"

"  hello   world "
→ "world hello"

1 先整体反转
2 再逐个单词反转

reverse()