左旋转字符串

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题目：

解法：

// 1、字符串切片
class Solution {
    public String reverseLeftWords(String s, int n) {
        String s1 = s.substring(0, n);
        String s2 = s.substring(n,s.length());
        String s3 = s2 + s1;
        return s3;
    }
}

// 2、列表遍历拼接
class Solution2 {
    public String reverseLeftWords(String s, int n) {
        StringBuilder s3 = new StringBuilder();
        for (int i = n; i < s.length(); i++) {
            s3.append(s.charAt(i));
        }
        for (int i = 0; i < n; i++) {
            s3.append(s.charAt(i));
        }

        return s3.toString();
    }
}

// 3、字符串遍历拼接
class Solution3 {
    public String reverseLeftWords(String s, int n) {
        String s3 = new String();
        for (int i = n; i < s.length(); i++) {
            s3 += s.charAt(i);
        }
        for (int i = 0; i < n; i++) {
            s3 += s.charAt(i);
        }

        return s3;
    }
}