22. Microsoft interview questions: Left-hand string

Question:

Define the left rotation operation of the string: Move several characters before the string to the end of the string.

For example, the string "abcdef" is left-byte 2 to get the string "cdefab ". Please implement the left rotation function of the string.

Requires O (n) for the complexity of string operations with a length of n, and the auxiliary memory is O (1 ).

Analysis:

The difficulty of this question is that the secondary memory can only use O (1), which is equivalent to only replacing the characters in the string. To move the string, m * n replacement operations are required, this complexity also comes up, O (n * n ).

You can only think about skills.

The implementation is as follows:

#include
  
   #include
   
    using namespace std;void reverse(char* str, int i, int j){        while( i < j)        {                char chr = str[i];                str[i] = str[j];                str[j] = chr;                i ++;                j --;        }}void leftRotate(char* srcstr, int k){        int len = strlen(srcstr);         if(len <= 1)                return;        k = k%len;        reverse(srcstr, 0, k - 1);        reverse(srcstr, k, len -1);        reverse(srcstr, 0, len -1);}int main(){        char str[] = "abcdef";        cout << "string: " << str << endl;        leftRotate(str, 2);        cout << "rotate string, 2: " << str << endl;        return 0;}
   
  

The output result is as follows:

String: abcdef
Rotate string, 2: cdefab