剑指offer-2.25-58.2

class Solution {
    
    
    public String reverseLeftWords(String s, int n) {
    
    
        return s.substring(n, s.length()) + s.substring(0, n);
    }
}

class Solution {
    
    
    public String reverseLeftWords(String s, int n) {
    
    
        int len = s.length();
        char[] str = s.toCharArray();
        for (int i = 0; i < n; i++) {
    
    
            char temp = str[0];
            for (int j = 0; j < len - 1; j++) {
    
    
                str[j] = str[j + 1];
            }
            str[len - 1] = temp;
        }
        return new String(str);
    }
}

class Solution {
    
    

    public void reverse(char[] str, int start, int end) {
    
    
		while (start < end) {
    
    
			char temp = str[start];
			str[start] = str[end];
			str[end] = temp;
			start++;
			end--;
		}
	}

    public String reverseLeftWords(String s, int n) {
    
    
        int len = s.length();
        char[] str = s.toCharArray();
        reverse(str, 0, n - 1);
        reverse(str, n, len - 1);
        reverse(str, 0, len - 1);
        return new String(str);
    }
}