message: Update missing-ranges.cpp
diff: @@ -5,9 +5,9 @@ class Solution {
  public:
  vector<string> findMissingRanges(vector<int>& nums, int lower, int upper) {
  vector<string> ranges;
  - for (int i = 0, pre = lower - 1, cur = 0; i <= nums.size(); ++i, pre = cur) {
  + for (int64_t i = 0, pre = static_cast<int64_t>(lower) - 1, cur = 0; i <= nums.size(); ++i, pre = cur) {
  if (i == nums.size()) {
  - cur = upper + 1;
  + cur = static_cast<int64_t>(upper) + 1;
  } else {
  cur = nums[i];
  }
  @@ -18,6 +18,7 @@ public:
  return ranges;
  }
  +private:
  string getRange(const int lower, const int upper) {
  if (lower == upper) {
  return to_string(lower);
  