【leetcode】Excel表列名称

char * convertToTitle(int n){
    char* arr = (char*)calloc(1002, sizeof(char));
    int val,pst=1001;
    while (n){
        val = n % 26;
        if (val == 0)
            val = 26;
        arr[--pst] = 'A' + val - 1;
        n = (n-val)/26;
    }    
    return arr+pst;
}