バイナリ検索とシーケンシャル検索を比較するC++プログラム

バイナリ検索とシーケンシャルまたはリニア検索はどちらも、コンピュータプログラミングで要素を検索するために使用されます。二分探索の時間計算量はO（log（n））であり、順次探索はO（n）です。

アルゴリズム

Begin
   Algorithm for Binary Search:
   BinarySearch() function with ‘arr’ the array of data and ‘n’ the number of values, start and end index, iteration count and element to be searched in the argument list.
   Increment iteration counter and compare the item value with the a[mid].
   If item < a[mid] choose first half otherwise second half to proceed further.
   Return iteration value on successful search.
End

サンプルコード

#include<iostream>
using namespace std;
int BinarySearch(int a[], int start, int end, int item, int iter) {
   int i, mid;
   cout<<"\niteration "<<iter+1;
   iter++;
   mid = start + (end-start+1)/2;
   if(item > a[end] || item < a[start] || mid == end) {
      cout<<"\nNot found";
      return iter;
   } else if(item == a[mid]) {
      cout<<"\n item found at "<<mid<<" index.";
      return iter;
   } else if(item == a[start]) {
      cout<<"\n item found at "<<start<<" index.";
      return iter;
   } else if(item == a[end]) {
      cout<<"\n item found at "<<end<<" index.";
      return iter;
   } else if(item > a[mid])
         BinarySearch(a, mid, 9, item, iter);
      else
         BinarySearch(a, start, mid, item, iter);
   }
   int LinearSearch(int a[], int n, int item) {
      int i;
      for(i = 0; i < n; i++) {
         cout<<"\niteration "<<i+1;
         if(a[i] == item) {
            cout<<"\n item found at "<<i<<" index.";
         return i+1;
      }
   }
   cout<<"\nNot found";
}
int main() {
   int n, i, B, L, a[10]={2, 7, 14, 24, 26, 35, 38, 41, 49, 53};
   cout<<"\nEnter the element to be searched: ";
   cin>>n;
   cout<<"\n\n\t\t\tBinary Search :";
   B = BinarySearch(a, 0, 9, n, 0);
   cout<<"\n\n\t\t\tLinear Search :";
   L = LinearSearch(a, 10, n);
   if(L > B)
      cout<<"\n\nBinary search is better for this search.";
   else if(L < B)
      cout<<"\n\nLinear search is better for this search.";
   else
      cout<<"\n\nBoth are equally efficient for this search.";
   return 0;
}

出力

Enter the element to be searched: 7
Binary Search :
iteration 1
iteration 2
iteration 3
iteration 4
item found at 1 index.
Linear Search :
iteration 1
iteration 2
item found at 1 index.
Linear search is better for this search.
Enter the element to be searched: 53
Binary Search :
iteration 1
item found at 9 index.
Linear Search :
iteration 1
iteration 2
iteration 3
iteration 4
iteration 5
iteration 6
iteration 7
iteration 8
iteration 9
iteration 10
item found at 9 index.
Binary search is better for this search.
Enter the element to be searched: 1
Binary Search :
iteration 1
Not found
Linear Search :
iteration 1
iteration 2
iteration 3
iteration 4
iteration 5
iteration 6
iteration 7
iteration 8
iteration 9
iteration 10
Not found
Binary search is better for this search.