[Leetcode] Count and Say

Count and Say 

The count-and-say sequence is the sequence of integers beginning as follows:
1, 11, 21, 1211, 111221, ...

1 is read off as "one 1" or 11.
11 is read off as "two 1s" or 21.
21 is read off as "one 2, then one 1" or 1211.

Given an integer n, generate the n^th sequence.

Note: The sequence of integers will be represented as a string.

» Solve this problem

 不知道怎么回事，用strcat就老是会有run error。

class Solution {
public:
    char buf[10000];
    char dest[10000];

    string countAndSay(int n) {
        
        buf[0] = '1';
        buf[1] = '\0';
        for (int i = 1; i < n; i++) {
            convert(buf, dest);
            memcpy(buf, dest, sizeof(buf));
        }
        return string(buf);
    }
    
    void convert(char* src, char* dest) {
        char num[10000];
        int cnt[10000];
        memset(cnt, 0, sizeof(cnt));
        memset(num, 0, sizeof(num));
        int idx = -1;
        int len = strlen(src);
        char *s = src, *end = src + len;
        char prev = 'x';
        while (s != end) {
            if (prev == *s) {
                cnt[idx]++;
            } else {
                cnt[++idx] = 1;
                num[idx] = *s;
                prev = *s;
            }
            s++;
        }
        
        int id = 0;
        char tmp[32];
        for (int i = 0; i <= idx; i++) {
            dest[id++] = cnt[i] + '0';
            dest[id++] = num[i];
        }
        dest[id] = '\0';
        return;
    }
};