201707 CSE110 Lecture 29
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This document discusses sorting algorithms in Java. It begins with an explanation of bubble sort, including a basic implementation and a more efficient version. It then covers selection sort, describing the algorithm, providing examples, and including an implementation in Java. The document is from a CSE110 class on principles of programming taught by Javier Gonzalez-Sanchez in the summer of 2017.
![Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 2
Bubble sort
public static void bubbleSort(int[] array1) {
boolean swap;
do {
swap = false;
for (int index=0;index<=array1.length-2;index++) {
// compare element at index and at index+1
if (array1[index] > array1[index+1])
{
//swap them if they are not in the order
int temp = array1[index+1];
array1[index+1] = array1[index];
array1[index] = temp;
swap = true
}
}
} while (swap == true);
}](https://image.slidesharecdn.com/cse110l29-sorting-170708045744/85/201707-CSE110-Lecture-29-2-320.jpg)
![Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 4
More Efficient Bubble sort
//More efficient version of Bubble Sort
public static void bubbleSort2(int[ ] array1) {
for(int position=array1.length-2; position>=0; position--) {
for (int index=0; index<=position; index++) {
//compare the element at index and at index+1
if (array1[index] > array1[index+1]){
//swap them if they are not in the order
int temp = array1[index+1];
array1[index+1] = array1[index];
array1[index] = temp;
}
}
}
}](https://image.slidesharecdn.com/cse110l29-sorting-170708045744/85/201707-CSE110-Lecture-29-4-320.jpg)
![Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 10
Selection Sort
public static void selectionSort (int[] data) {
int minIndex;
for (int index=0; index<data.length-1; index++) {
minIndex = index;
for (int scan=index+1;scan<data.length; scan++){
if (data[scan] < data[minIndex]) {
minIndex = scan;
}
}
//swap the two elements, data[minIndex] and data[index]
int temp = data[minIndex];
data[minIndex] = data[index];
data[index] = temp;
}
}](https://image.slidesharecdn.com/cse110l29-sorting-170708045744/85/201707-CSE110-Lecture-29-10-320.jpg)
201707 CSE110 Lecture 29
- 1. CSE110 Principles of Programming with Java Lecture 29: Sorting Javier Gonzalez-Sanchez javiergs@asu.edu javiergs.engineering.asu.edu Office Hours: By appointment
- 2. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 2 Bubble sort public static void bubbleSort(int[] array1) { boolean swap; do { swap = false; for (int index=0;index<=array1.length-2;index++) { // compare element at index and at index+1 if (array1[index] > array1[index+1]) { //swap them if they are not in the order int temp = array1[index+1]; array1[index+1] = array1[index]; array1[index] = temp; swap = true } } } while (swap == true); }
- 3. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 3 More Efficient Bubble sort • Notice that after the 1st pass, the largest element is placed in its final position (right most location). • That indicates that after the 2nd pass, the second largest element will be placed in its final position and so on. • So we can reduce the number of comparisons by 1 for every pass. • If we have n elements in the array, then the 1st pass requires (n-1) comparisons, the second pass requires (n-2) comparisons, and so on.
- 4. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 4 More Efficient Bubble sort //More efficient version of Bubble Sort public static void bubbleSort2(int[ ] array1) { for(int position=array1.length-2; position>=0; position--) { for (int index=0; index<=position; index++) { //compare the element at index and at index+1 if (array1[index] > array1[index+1]){ //swap them if they are not in the order int temp = array1[index+1]; array1[index+1] = array1[index]; array1[index] = temp; } } } }
- 6. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 6 Algorithm 1. Selection Sort locates the smallest element in the array and exchanges it with the element in position 0. 2. It locates the next smallest element in the array and exchanges it with the element in position 1. 3. It continues until all elements are in order.
- 7. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 7 Example 1
- 8. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 8 Example 1
- 9. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 9 Example 2
- 10. Javier Gonzalez-Sanchez | CSE110 | Summer 2017 | 10 Selection Sort public static void selectionSort (int[] data) { int minIndex; for (int index=0; index<data.length-1; index++) { minIndex = index; for (int scan=index+1;scan<data.length; scan++){ if (data[scan] < data[minIndex]) { minIndex = scan; } } //swap the two elements, data[minIndex] and data[index] int temp = data[minIndex]; data[minIndex] = data[index]; data[index] = temp; } }
- 11. CSE110 - Principles of Programming Javier Gonzalez-Sanchez javiergs@asu.edu Summer 2017 Disclaimer. These slides can only be used as study material for the class CSE110 at ASU. They cannot be distributed or used for another purpose.