C语言编程学习课件 (31).pdf

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1、Programming In CProgramming In C Sequential Search The sequential search,also known as linear search.Start with the first number of the data list and search the number one by one.5 21 23 10 7 15 18 2 6 20 For example,the number we entered from the keyboard is 7.Then the searching process is as shown

2、 above.Assuming there is a data list:7 not equal 7 equal In this way,we find the number 7 in the data list,and we can determine that it is the third element.Sequential Search 5 21 23 10 7 15 18 2 6 20 For example,the number we entered from the keyboard is 25.Then the searching process is as shown be

3、low.However,what if the number we entered from the keyboard is not in the data list?25 not equal In this way,no element equal to 25 has been found in the data list.Code Running result 7 The position of 7 is:3 Running result 25 The number is not found!Binary Search Here I will introduce to you a more

4、 efficient searching method:binary search.A necessary premise for binary search is that the data list should be an ordered sequence.That is,the data list is arranged in ascending or descending order.For example,there is such a sequence data.Suppose we want to search 16 in the sequence.We first compa

5、re 16 with the number 13 in the middle of the sequence.Because 16 is bigger than 13,it will never appear in a position smaller than 13.That means 16 will be in the right half of the sequence.16 not equal should go this way Binary Search Therefore,we exclude the first half of the sequence and do a binary search on the second half of the sequence.Because 16 is in the middle of the second half,compare the values of them,then we find it.So we find it.16 not equal 16 equal Code Running result 16 The position of 16 is:7 Programming In CProgramming In C