Delete BinarySearchIn2DArrays.cpp
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// C++ program to implement Binary Search in 2D Arrays
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#include <iostream>
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#include <vector>
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using namespace std;
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// Floor of a array is the greatest number which is smaller than or equal to the target element
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// Search the floor number in the first column. Since the array is sorted that means the target element
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// should lie on the row which has the first element as its floor
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int Floor(vector<vector<int>> arr, int target)
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{
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int start = 0;
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int end = arr.size() - 1;
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if(target < arr[start][0])
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return arr[start][0];
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while (start <= end)
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{
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int mid = start + (end - start) / 2;
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if(target < arr[mid][0])
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end = mid - 1;
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else if(target > arr[mid][0])
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start = mid + 1;
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else
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return mid; // if it is the target element return the column index
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}
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return end; // Since the condition in which the loop breaks is start > end that means the end will be smaller than target element
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// whereas start will be greater than target element.
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}
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// Search just in a row which has its first element smaller than or equal to target element(floor)
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vector<int> BinarySearch(vector<vector<int>> arr, int target)
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{
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int floor = Floor(arr, target);
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int start = 0;
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int end = arr[floor].size() - 1;
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while(start <= end)
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{
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int mid = start + (end - start) / 2;
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if(target > arr[floor][mid])
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start = mid + 1;
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else if(target < arr[floor][mid])
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end = mid - 1;
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else
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return {floor, mid};
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}
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return {-1 , -1}; // If element is not found return negatives.
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}
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int main(int argc, char const *argv[])
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{
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vector<vector<int>> arr = {
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{1,2,3,4},
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{5,6,7,8},
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{9,10,11,12},
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{13,14,15,16}
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};
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vector<int> ans = BinarySearch(arr, 15);
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cout << "[ " << ans[0] << " , " << ans[1] << " ]" << endl; // [3, 2] for such target element
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return 0;
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}
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