47 lines
1.0 KiB
C++
47 lines
1.0 KiB
C++
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/*
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Exponential search involves two steps, first to find the range within
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which the element is found and searching inside that range using
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binary search.
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*/
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#include <iostream>
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#include <vector>
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int binary_search(std::vector<int> arr, int item, int low, int high){
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int mid;
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while(low <= high){
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mid = low + (high - low)/2;
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if(arr[mid] == item){ return mid; }
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else if(arr[mid] < item){ low = mid + 1; }
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else{ high = mid - 1;}
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}
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return -1;
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}
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int exponential_search(std::vector<int> arr, int item){
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int k = 1;
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int size = arr.size() - 1;
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while(k < size && arr[k] <= item){ k *= 2; }
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return binary_search(arr, item, k/2, std::min(k, size));
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}
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int main(){
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std::vector<int> arr;
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for(int i=1; i<30; i+=2){ arr.push_back(i); }
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for(int i=0; i<arr.size(); i++){ std::cout << arr[i] << " "; }
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std::cout << std::endl;
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int index = exponential_search(arr, 15);
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std::cout << "Index of 15: " << index << std::endl;
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/*
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Output:
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1 3 5 7 9 11 13 15 17 19 21 23 25 27 29
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Index of 15: 7
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Time Complexity: O(log(n))
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*/
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return 0;
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}
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