The number of occurrences in a sorted array of "sword point 38"

Ideas:

Using the binary search, we find the index of the head and tail of the statistic, and the result is the difference of the last one.

C++:

1#include <iostream>2#include <vector>3 using namespacestd;4 5 intGETFIRSTK (vector<int>& Nums,intStartpos,intEndpos,intk)6 {7     if(Startpos >endpos)8         return-1;9 Ten     intMid = (startpos + endpos)/2; One  A     if(Nums[mid] = =k) -     { -         if(Mid = =0|| (Mid >0&& Nums[mid-1] !=k)) the             returnmid; -         Else -Endpos = mid-1; -     } +     Else if(Nums[mid] <k) -     { +Startpos = mid +1; A     } at     Else -     { -Endpos = mid-1; -     } -  -     returnGetfirstk (Nums, Startpos, Endpos, k); in } -  to intGETLASTK (vector<int>& Nums,intStartpos,intEndpos,intk) + { -     if(Startpos >endpos) the         return-1; *  $     intMid = (startpos + endpos)/2;Panax Notoginseng     intLastpos = Nums.size ()-1; -  the     if(Nums[mid] = =k) +     { A         if(Mid = = Lastpos | | (Mid < Lastpos && Nums[mid +1] !=k)) the             returnmid; +         Else -Startpos = mid +1; $     } $     Else if(Nums[mid] <k) -     { -Startpos = mid +1; the     } -     ElseWuyi     { theEndpos = mid-1; -     } Wu  -     returnGetlastk (Nums, Startpos, Endpos, k); About } $  - intMain () - { -     inta[Ten] = {1,2,3,3,3,3,3,4,4,5}; Avector<int> V (A, A +Ten); +  theCout<<getlastk (V,0,9,4)-Getfirstk (V,0,9,4) +1<<Endl; -}

The number of occurrences in a sorted array of "sword point 38"