LC 163. Missing Ranges 【lock, hard】

Given a sorted integer array nums, where the range of elements are in the inclusive range [lower, upper], return its missing ranges.

example:

Input: nums = [0, 1, 3, 50, 75], lower = 0 and upper = 99,
Output: ["2", "4->49", "51->74", "76->99"]

这题应该是实现的细节处理，最大整数，最小整数比较难，也是调了很久的corner case才调出来的。

好不容易Accept了，自己写的还是有点惨。

还要注意

if(lower++ == something) something;

不管判断对不对，lower都会自增的，要当心。

AC第一版

 #include <iostream>
 #include <vector>
 using namespace std;
 struct TreeNode {
     int val;
     TreeNode *left;
     TreeNode *right;
     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 };

 vector<string> findMissingRanges(vector<int>& nums, int lower, int upper) {
   vector<string> ret;
   vector<int> processed;
   for(int i=; i<nums.size(); i++){
     if(processed.empty() || processed.back() != nums[i]){
       processed.push_back(nums[i]);
     }
   }
   nums.clear();
   //for(auto i : processed) nums.push_back(i);

   for(auto i : processed) cout << i << " ";
   cout << endl;
   nums = processed;
   if(lower == upper) {
     if(!nums.empty()) return ret;
     else ret.push_back(to_string(lower));
     return ret;
   }
   if(nums.empty()){
     ret.push_back(to_string(lower) + "->" + to_string(upper));
     return ret;
   }
   for(int i=; i<nums.size(); i++){
     //cout << lower << "and" << nums[i] << endl;
     if (lower == nums[i]) {
       lower++;
       continue;
     }

     if(lower+ == nums[i]) ret.push_back(to_string(lower));
     else ret.push_back(to_string(lower) + "->" + to_string(nums[i]-));
     if(nums[i] == ( << )-) return ret;
     lower = nums[i]+;
   }
   //cout << lower << upper << endl;
   if(lower > upper) return ret;
   if(lower == upper) ret.push_back(to_string(lower));
   else ret.push_back(to_string(lower) + "->" + to_string(upper));
   return ret;
 }

AC 第二版

简化了一些代码

vector<string> findMissingRanges(vector<int>& nums, int lower, int upper) {
  vector<string> ret;
  vector<int> processed;
  // filter duplicate
  for(auto val : nums) {
    if(processed.empty() || processed.back() != val) processed.push_back(val);
  }
  nums.clear();
  nums = processed;
//   for(auto i : processed) cout << i << " ";
//   cout << endl;
  // corner case 1: lower == upper
  if(lower == upper) {
    if(nums.empty()) ret.push_back(to_string(lower));
    return ret;
  }
  for(int i=; i<nums.size(); i++){
    if (lower != nums[i]) {
      if(lower+ == nums[i]) ret.push_back(to_string(lower));
      else ret.push_back(to_string(lower) + "->" + to_string(nums[i]-));
    }
    if(nums[i] == ( << )-) return ret;
    lower = nums[i]+;
  }
  //cout << lower << upper << endl;
  if(lower == upper) ret.push_back(to_string(lower));
  else if(lower < upper) ret.push_back(to_string(lower) + "->" + to_string(upper));
  return ret;
}