Missing Ranges in C++

Suppose we have a sorted integer array nums, the range of elements are in the inclusive range [lower, upper], we have to find the missing ranges.

So, if the input is like nums = [0, 1, 3, 50, 75], and lower value is 0 and upper value is 99, then the output will be ["2", "4->49", "51->74", "76->99"]

To solve this, we will follow these steps −

• Define an array nums

• Define one set v

• for initialize i := 0, when i < size of t, update (increase i by 1), do −

  • if t[i] is not in v, then −

    • insert t[i] into v

    • insert t[i] at the end of nums

• define one array called ret

• curr := lower

• i := 0, n := size of nums

• while curr <= upper, do −

  • if i < n and nums[i] is same as curr, then −

    • (increase i by 1)

    • (increase curr by 1)

  • Otherwise

    • temp := convert curr to string

    • (increase curr by 1)

    • if i < n and nums[i] is same as curr, then −

      • insert temp at the end of ret

      • Ignore following part, skip to the next iteration

    • Otherwise

      • if i is same as n, then −

        • if curr <= upper, then −

          • temp := "->"

          • temp := temp concatenate upper as string

          • curr := upper + 1

        • insert temp at the end of ret

      • Otherwise

        • temp := "->"

        • curr := nums[i]

        • temp := temp concatenate (curr - 1) as string

        • curr := nums[i]

        • insert temp at the end of ret

• return ret

Example 

Let us see the following implementation to get a better understanding −

 Live Demo

#include <bits/stdc++.h>
using namespace std;
void print_vector(vector<auto< v){
   cout << "[";
   for(int i = 0; i<v.size(); i++){
      cout << v[i] << ", ";
   }
   cout << "]"<<endl;
}
class Solution {
public:
   vector<string< findMissingRanges(vector<int<& t, int lower, int upper) {
      vector <int< nums;
      set <long long int> v;
      for(int i = 0; i < t.size(); i++){
         if(!v.count(t[i])){
            v.insert(t[i]);
            nums.push_back(t[i]);
         }
      }
      vector < string > ret;
      long long int curr = lower;
      int i = 0;
      int n = nums.size();
      while(curr <= upper){
         if(i < n && nums[i] == curr){
            i++;
            curr++;
         }
         else{
            string temp = to_string(curr);
            curr++;
            if(i < n && nums[i] == curr){
               ret.push_back(temp);
               continue;
            }
            else{
               if(i == n){
                  if(curr <= upper){
                     temp += "->";
                     temp += to_string(upper);
                     curr = (long long int )upper + 1;
                  }
                  ret.push_back(temp);
               }
               else{
                  temp += "->";
                  curr = nums[i];
                  temp += to_string(curr - 1);
                  curr = nums[i];
                  ret.push_back(temp);
               }
            }
         }
      }
      return ret;
   }
};
main(){
   Solution ob;
   vector<int< v = {0,1,3,50,75};
   print_vector(ob.findMissingRanges(v, 0, 99));
}

Input

{0,1,3,50,75}, 0, 99

Output

[2, 4->49, 51->74, 76->99, ]