剑指OFFER 左旋转字符串

Posted 2021-03-16 virgildevil

剑指OFFER 左旋转字符串

方法1:新创建一个字符串

class Solution {
public:
    string LeftRotateString(string str, int n) {
        string res;
        int len = str.size();
        for(int i=n;i<len+n;i++)
        {
            res.push_back(str[i%len]);
        }
        return res;
    }
};

写得十分简洁了,比当时第一次写这种类型的题的时候进步很大了.

方法2:直接在原字符串上进行修改

与这道题类似,这道题是右旋转

稍加修改就可以通过了

class Solution {
public:
    void rotateStr(string &str,int left,int right)
    {
        while (left < right)
        {
            char  tc = str[left];
            str[left] = str[right];
            str[right] = tc;
            left++;
            right--;
        }
    }
    string LeftRotateString(string str, int n) {
        int len = str.length();
        if(len==0)return string("");
        int new_offset = len - n;
        rotateStr(str, 0, len-new_offset-1);
        rotateStr(str, len-new_offset, len-1);
        rotateStr(str, 0, len-1);
        return str;
    }
};