1556. 千位分隔数

C代码：

char * thousandSeparator(int n){
    char* str = (char*)malloc(sizeof(char) * 20);
    int len = sprintf(str, "%d", n);
    int len2 = 0;
    if (len % 3 == 0) {
        len2 = len+ len / 3 - 1;
    } else {
        len2 = len + len / 3;
    }
    char* ans = (char*)malloc(sizeof(char) * (len2 + 1));
    ans[len2] = '\0';

    for(int i = len - 1; i >= 0; --i) {
        if (len - 1 - i != 0 && (len - 1 - i) % 3 == 0) {
            ans[--len2] = '.';
        }
        ans[--len2] = str[i];
    }
    return ans;
}

Java代码：

class Solution {
    public String thousandSeparator(int n) {
        int count = 0;
        StringBuffer ans = new StringBuffer();
        do {
            int cur = n % 10;
            n /= 10;
            ans.append(cur);
            ++count;
            if (count % 3 == 0 && n != 0) {
                ans.append('.');
            }
        } while (n != 0);
        ans.reverse();
        return ans.toString();
    }
}