数据结构与算法设计实验课程01

Original sequence： [7] 4 -2 19 13 6
1st process： [4
2nd process： [-2 3rd process： [-2 4th process： [-2 5th process： [-2
7]
4 4 4 4
-2
7] 7 7 6
19
19 19] 13 7
13
Sort Process
Suppose the initial sequence as R[s…t] ，set any item as pivot(usually use R[s])，reorder the rest of items according to R[s].key, when compared to R[s].key： • Put the records with smaller keys before R[s] ； • Put the records with bigger keys after R[s] ； Set the R[s].key’s latest position as boundary, sequence R[s…t] are separated into two sequences. Then complete one-pass quick sort.
Selection sort
E.g. Sequence：7, 4, -2, 19, 13, 6，Simple selection sort,
Original sequence： 7 4 -2 19 13 6
1st process：-2
2nd process： -2 3rd process： -2 4th process： -2 5th process： -2 6th process： -2
4
4 4 4 4 4
7
7 6 6 6 6
19
19 19 7 7 7
13
13 13 13 13 13
6
6 7 19 19 19
Quick sort
Ideology: Quicksort is a divide and conquer algorithm
first divides a large array into two smaller sub-arrays. Each item in one part is always smaller than the items in the other part. Continue this process on two sub-arrays respectively, until the all the items are ordered .
Data Structures & Algorithm Design (1)
Sort
Ying Zhang College of Software, Nankai University
Implementation & Performance
Implement the Sort Algorithms
Generate random array
#include <iostream> #include <cstdlib> #include <ctime> using namespace std;
int main() { srand ( time (NULL) ); int N=1000; for ( int i = 0 ; i < N; i ++ ) cout << rand() % 100 << "\t" ; cout << endl; return 0; }
Insertion Sort Bubble Sort Selection Sort Quick Sort
Generate test data randomly Output the result of each sorting process
Implementation & Performance
Count the time consumption
#include <ctime> #include <iostream> using namespace std; void main() { clock_t start, end; double dif; start = clock(); ………//calculate process end = clock(); dif = end - start; cout << " time consumed " << dif/CLOCKS_PER_SEC << " seconds. " << endl; }
41
41 41
45
45 45
67
67 67
Selection sort
selecting the minimum item from the list to be sorted, and put it in the front of the list to be sorted; Repeat this step until no elements in the list to be sorted Simple Selection Sort ：select the minimum item from n-i+1 records by comparing n-i times，then swap with the ith item ，i=1, 2, … n-1 。
13 13 19] 13
6
6 6 6 19]
Bubble sort
Repeatedly stepping through the list to be sorted comparing each pair of adjacent elements and swapping them if they are in the wrong order (left>right). At the end of one bubbling pass, we are assured that the largest(smallest) element is in the rightmost position. The pass through the list is repeated until no swaps are needed, which indicates that the list is sorted
Insertion sort
Each iteration, removes one element Ri from the input data, find the location it belongs within the sorted record sequence R1, R2 ,…., Ri-1, and insert it there. It repeats until no input elements remain. E.g. suppose sequence 7, 4, -2, 19, 13, 6，sorting process
100，1000，10000，100000，1000000
Experimental report
Deadline Assign Time
Oct. 9, 2014
Submit Deadline
Oct. 21, 2014 23:59
Submit to
One-pass quick sort
Set two pointers with the initial value low and high respectively set the key value of pivot item is pivotkey. First, search forward from the position of high pointer, find the first item whose key is smaller than pivotkey, then swap it with pivot. Then, search backword from the positon of low pointer, find the first item whose key is bigger than pivotkey, then swap it with pivot. Repeat these two steps until low = high.
2nd process:
3rd process: 4th process: 5th process: 6th process: 7th process:
22
22
23
23
23
23
31
15
15
31
38
38
41
41
45
45
67
67
22
22 15
23
15 22
15
23 23
23
23 23Βιβλιοθήκη 3131 3138
38 38
Sort
Sorting is an operations based on key non-decreasing or non-increasing order to rearrange the set of records . Suppose sequence contains n records : {r1, r2, … ,rn}, their corresponding keywords are {k1, k2, … ,kn}. Define an array p1, p2,…,pn for the serial number 1 ,2, …,n, to make the corresponding keywords meet the following non-decreasing (increasing) relationship：kp1≤ kp2 ≤ … ≤ kpn The keyword ki can be either the primary key of record sequence or secondary key, or combination of several items.