LintCode: Count and Say

C++

class Solution {
public:
    /**
     * @param n the nth
     * @return the nth sequence
     */
    string countAndSay(int n) {
        // Write your code here
        if (0 == n) {
            return "";
        }
        string pre = "1";
        for (int i = 1; i < n; i++) {//从第2个（i=1）开始
            char ch = pre[0];
            string cur = "";
            int cnt = 0;
            for (int j = 0; j < pre.size(); j++) {
                if (pre[j] == ch) {
                    cnt ++;
                } else {
                    cur = cur + itostr(cnt) + ch;
                    ch = pre[j];
                    cnt = 1;
                }
            }
            if (cnt != 0) {//处理后边的字符
                cur = cur + itostr(cnt) + ch;
            }
            pre = cur;
            cur = "";
        }
        return pre;
        
    }
    string itostr(int i) {//自定义int转string函数
        char str[10];
        //itoa(str,i,10);->only support Windows
        sprintf(str, "%d", i);//support any platforms
        return str;
    }
};