CS Notes 6

CS Notes 6 - o Best with linked lists o Once it is matched,...

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Searching Wednesday, February 02, 2011 4:19 PM Sequential (Linear) Search Successful search Worst case: O(n) Best case : O(1) Average: O(n/2)->No constants->O(n) Basic Op: Comparing target against item in data structure Failures Worst case: O(n) Best Case: O(n) Average Case: O(n) Average analysis What is the # of comparisons? o [1+2+3+…+n]/n=[n(n+1)]/2 o (n+1)/2 o Using 'real' average time to improve performance n-1 o Avg= Σ probability * position of element i=0 o Rearrange array items in decreasing order of probabilities Adaptive ways to improve search time 1. When a match is found, move item to front
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Unformatted text preview: o Best with linked lists o Once it is matched, it is likely that it will be searched again 1. Move one spot towards front o Less extreme than 1 Binary Search Only applies to sorted arrays Divide and conquer Sorted array 5 10 15 20 25 30 35 40 45 1 2 3 4 5 6 7 8 low Mid High Target= 40 40!=25 40>25 Public static boolean binarySearch (int list, int target) { Int lo=0, hi=list.length-1; While( lo <=hi) { Int mid= (lo+hi)/2; If (target==list[mid]) { Return true; } If (target < list [mid) { Hi=mid-1; } else { Lo=mid+1; } } Return false; }...
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This note was uploaded on 02/29/2012 for the course 198 112 taught by Professor Venugopal during the Spring '09 term at Rutgers.

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CS Notes 6 - o Best with linked lists o Once it is matched,...

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