剑指Offer之Java算法习题精讲字符串与二叉搜索树

class Solution {
    public boolean repeatedSubstringPattern(String a) {
        for (int i = 1; i <=a.length()/2 ; i++) {
            String s = a.substring(0, i);
            StringBuffer sb = new StringBuffer();
            while (sb.length()<a.length()){
                sb.append(s);
            }
            if(sb.toString().equals(a)){
                return true;
            }
        }
        return false;
    }
}

class Solution {
    public boolean detectCapitalUse(String Word) {
        if(word.toLowerCase().equals(word)||word.toUpperCase().equals(word)||word.substring(1, word.length()).toLowerCase().equals(word.substring(1, word.length()))) return true;
        return false;
    }
}

class Solution {
    int ans;
    int pre;
    public int getMinimumDifference(Treenode root) {
        ans = Integer.MAX_VALUE;
        pre = -1;
        method(root);
        return ans;
    }
    public void method(TreeNode root){
        if(root==null){
            return;
        }
        method(root.left);
        if(pre==-1){
            pre = root.val;
        }else{
            ans = Math.min(ans, root.val - pre);
            pre = root.val;
        }
        method(root.right);
    }
}

class Solution {
    public String reverseStr(String a, int k) {
        int con = 1;
        StringBuffer sb = new StringBuffer();
        while (con*k<=a.length()){
            String substring = a.substring((con - 1) * k, con * k);
            if(con%2==0){
                sb.append(substring);
                con++;
            }else {
                for (int i1 = substring.length()-1; i1 >=0 ; i1--) {
                    sb.append(substring.charAt(i1));
                }
                con++;
            }
        }
        if((con-1)*k<a.length()){
            String s = a.substring((con-1) * k, a.length());
            if(con%2!=0){
                for (int i1 = s.length()-1; i1>=0; i1--) {
                    sb.append(s.charAt(i1));
                }
            }else {
                sb.append(s);
            }
        }
        return sb.toString();
    }
}