【leetcode】删除最外层的括号

char * removeOuterParentheses(char * S){
    int len = strlen(S),count=1,n=0;
    char* ret = (char*)calloc(len,sizeof(char*));
    for (int i=1; i<len; i++)
    {
        (S[i] == '(')? count++: count--;
        if(count) ret[n++] = S[i];
        else count=1,i++; 
    }
    return ret;
}