Offer to prove safety study notes (C # and JS) - A string left rotation

Title Description

There is a shift in the assembly language instruction called a rotate left (the ROL), and now there is a simple task, this instruction is simulated by the string operation result. For a given character sequence S, you put its left circle after K-bit serial output. For example, the character sequence S = "abcXYZdef", rotated left required output result after three, i.e. "XYZdefabc". Is not it simple? OK, get it!

A. Resolve title

        The subject borrow a Remove function. Really want is more of a problem.

        For example sub-bar. ABC DEF - - DEF ABC (change the top three on the case)

        Remove two functions, first removing the top three; after removal of the second three. Finally, I would add to.

II. Code implementation

class Solution
{
    public string LeftRotateString(string str, int n)
    {
        // write code here
        if (n > str.Length || n == 0)
        {
            return str;
        }
        if (str == null)
        {
            return null;
        }
        int x = str.Length;
        string a = str.Remove(0,n);
        string b = str.Remove(n,str.Length-n);
        return (a+b);
    }
}