Count and Say

public class Solution {
    public String countAndSay(int n) {
        // Start typing your Java solution below
        // DO NOT write main() function
        ArrayList<Character> current = new ArrayList<Character>();
        current.add('1');
        for (int i = 1; i != n; ++i)
            current = next(current);
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < current.size(); ++i)
            sb.append(current.get(i));
        return sb.toString();
    }
    
    ArrayList<Character> next(ArrayList<Character> current){
        ArrayList<Character> tempList = new ArrayList<Character>();
        Character temp =  current.get(0);
        int count = 1;
        for (int i = 1; i < current.size()-1; ++i){
            if (!current.get(i).equals(temp)){
                add(tempList, count);
                tempList.add(temp);
                temp = current.get(i);
                count = 1;
            } else 
                count++;
        }
        if (current.size() > 1){
            if (current.get(current.size()-1).equals(temp)) {
                add(tempList, count+1);
                tempList.add(temp);
            } else {
                add(tempList, count);
                tempList.add(temp);
                add(tempList, new Character('1'));
                tempList.add(current.get(current.size()-1));
            }
        } else {
            add(tempList, count);
            tempList.add(temp);
        }
        return tempList;
    }
    
    ArrayList<Character> add(ArrayList<Character>temp, int i){
        if (i < 10){
            temp.add((char)(i+48));
            return temp;
        } else {
            temp = add(temp, i / 10);
            temp.add((char)(i % 10 + 48));
            return temp;
        }
            
    }
}

原来自己写了一个函数add，而且int强制转换char是要加48的（一开始不知道，囧），然后还runtime error了。后来发现Character类有toChars()方法，改写了一下试试，结果发现完全不对。。。好像是这个方法必须是utf-16的编码= = 还是继续改原来的方法好了

public class Solution {
    public String countAndSay(int n) {
        // Start typing your Java solution below
        // DO NOT write main() function
        ArrayList<Character> current = new ArrayList<Character>();
        current.add('1');
        for (int i = 1; i != n; ++i)
            current = next(current);
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < current.size(); ++i)
            sb.append(current.get(i));
        return sb.toString();
    }
    
    ArrayList<Character> next(ArrayList<Character> current){
        ArrayList<Character> tempList = new ArrayList<Character>();
        Character temp =  current.get(0);
        int count = 1;
        for (int i = 1; i < current.size()-1; ++i){
            if (!current.get(i).equals(temp)){
                add(tempList, count);
                tempList.add(temp);
                temp = current.get(i);
                count = 1;
            } else 
                count++;
        }
        if (current.size() > 1){
            if (current.get(current.size()-1).equals(temp)) {
                add(tempList, count+1);
                tempList.add(temp);
            } else {
                add(tempList, count);
                tempList.add(temp);
                add(tempList, 1);
                tempList.add(current.get(current.size()-1));
            }
        } else {
            add(tempList, count);
            tempList.add(temp);
        }
        return tempList;
    }
    
    ArrayList<Character> add(ArrayList<Character>temp, int i){
        if (i < 10){
            temp.add((char)('0' + i));
            return temp;
        } else {
            temp = add(temp, i / 10);
            temp.add((char)('0' + i % 10));
            return temp;
        } 
    }
}

吃饭去！！！