字符串 单词 翻转
Table of Contents
如将字符串"abcdef"的前两个字符翻转到后面变成"cdefab"。
整个字符串可以分为左边和右边两部分，翻转思路是：
- 将左边字符串反序（"ab"变成"ba"）
- 将右边字符串反序("cdef"变成"fedc")
- 左右部分反序后的组合是"bafedc"
- 最后将整个字符串反序（"bafedc"变成"cdefab"）得到我们要的结果
完整代码如下：
void invertStr(char str[], int start, int end)
{
while (end > start) {
char temp = str[start];
str[start] = str[end];
str[end] = temp;
++start;
--end;
}
}
void rotateStr(char str[], int len, int leftLen)
{
leftLen %= len;
invertStr(str, 0, leftLen - 1);
invertStr(str, leftLen, len - 1);
invertStr(str, 0, len - 1);
}
int _tmain(int argc, _TCHAR* argv[])
{
char str[] = "abcdef"; // defabc
std::cout << "before:" << str << std::endl;
rotateStr(str, strlen(str), 2);
std::cout << "after:" << str << std::endl;
system("pause");
return 0;
}
std::string版
class Solution {
public:
string LeftRotateString(string str, int n) {
if (str.empty()) {
return "";
}
n %= str.size();
Invert(str, 0, n - 1);
Invert(str, n, str.size() - 1);
Invert(str, 0, str.size() - 1);
return str;
}
void Invert(string &str, int from, int to) {
while (from < to) {
std::swap(str[from++], str[to--]);
}
}
};
单词翻转
class Solution {
public:
string ReverseSentence(string str) {
int index = 0;
for (int i = 0, count = str.size(); i < count; i++) {
if (str[i] == ' ') {
Invert(str, index, i - 1);
index = i + 1;
}
}
Invert(str, index, str.size() - 1);
Invert(str, 0, str.size() - 1);
return str;
}
void Invert(string &str, int from, int to) {
while (from < to) {
std::swap(str[from++], str[to--]);
}
}
};
如：I am a student翻转为student a am I