我有以下函数，找到4个数字和最大数字的最小总和：
void miniMaxSum(vector<int> arr) {
std::sort (arr.begin(), arr.end()); //(12 32 45 71)26 80 53 33
unsigned long long minSum = arr[0] + arr[1] + arr[2] + arr[3];
unsigned long long maxSum = (unsigned long long) arr[arr.size() - 1] + (unsigned long long) arr[arr.size() - 2] + (unsigned long long) arr[arr.size() - 3];
cout << arr[arr.size() - 1] << " " << arr[arr.size() - 2] << " " << arr[arr.size() - 3] << " " << arr[arr.size() - 4] << " " << endl;
cout << minSum << " " << maxSum << endl;
}
现在，如果我省略（unsigned long long）转换，我会溢出 . 有谁知道为什么？编译器不应该自动将int转换为unsigned long long吗？