Searching in DSA that follow a dsa searching.pptx

Searching in DSA that follow a dsa searching.pptx

• 1.
  : Mrs KeertiShrivastava ma’am_ (Ass. Professor of CSA)
• 2.
  Searching…? Searching in data-strucutrerefers to the process of finding a desired element in set of items. The desired element is called "target". The set of items to be searched in, can be any data-structure like − list, array, linked-list, tree or graph.
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  Searching Algorithm…  Linearor Sequential Search : A linear search or sequential search is a method for finding an element within a list. It sequentially checks each element of the list until a match is found or the whole list has been searched. Linear Search Binary Search
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  Algorithm… The basic stepsto perform Binary Search are: •Start from the leftmost element of arr[] and one by one compare x with each element of arr[] •If x matches with an element, return the index. •If x doesn’t match with any of the elements, return -1.
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  Program… #include <stdio.h> int search(intarr[], int N, int x) { int i; for (i = 0; i < N; i++) if (arr[i] == x) return i; return -1; } // Driver's code int main(void) { int arr[] = { 2, 3, 4, 10, 40 }; int x = 10; int N = sizeof(arr) / sizeof(arr[0]); // Function call int result = search(arr, N, x); (result == -1) ? printf("Element is not present in array") : printf("Element is present at index %d", result); return 0; } Element is present at index 3 Output
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  Searching Algorithm…  BinarySearch : Binary Search is a searching algorithm for finding an element's position in a sorted array. In this approach, the element is always searched in the middle of a portion of an array. Binary search can be implemented only on a sorted list of items. If the elements are not sorted already, we need to sort them first. Binary Search is a searching algorithm used in a sorted array by repeatedly dividing the search interval in half. The idea of binary search is to use the information that the array is sorted and reduce the time complexity to O(Log n).
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  Algorithm… The basic stepsto perform Binary Search are: •Begin with the mid element of the whole array as a search key. •If the value of the search key is equal to the item then return an index of the search key. •Or if the value of the search key is less than the item in the middle of the interval, narrow the interval to the lower half. •Otherwise, narrow it to the upper half. •Repeatedly check from the second point until the value is found or the interval is empty.
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  Program… // C programto implement recursive Binary Search #include <stdio.h> // A recursive binary search function. It returns // location of x in given array arr[l..r] is present, // otherwise -1 int binarySearch(int arr[], int l, int r, int x) { if (r >= l) { int mid = l + (r - l) / 2; // If the element is present at the middle // itself if (arr[mid] == x) return mid; // If element is smaller than mid, then // it can only be present in left subarray if (arr[mid] > x) return binarySearch(arr, l, mid - 1, x); // Else the element can only be present // in right subarray return binarySearch(arr, mid + 1, r, x); } // We reach here when element is not // present in array return -1; } int main(void) { int arr[] = { 2, 3, 4, 10, 40 }; int n = sizeof(arr) / sizeof(arr[0]); int x = 10; int result = binarySearch(arr, 0, n - 1, x); (result == -1) ? printf("Element is not present in array") : printf("Element is present at index %d", result); return 0; Output Element is present at index 3
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  Linear Vs BinarySearch_ a