Post on 19-Dec-2015
Selection SortingLecture 21
Selection Sort
• Given an array of length n,– In first iteration: Search elements 0 through
n-1 and select the smallest• Swap it with the element in location 0
– In second iteration: Search elements 1 through n-1 and select the smallest• Swap it with the element in location 1
– In third iteration: Search elements 2 through n-1 and select the smallest• Swap it with the element in location 2
– Continue in this fashion until there’s nothing left to search
Example and analysis of Selection Sort
• The Selection Sort might swap an array element with itself--this is harmless.
7 2 8 5 4
2 7 8 5 4
2 4 8 5 7
2 4 5 8 7
2 4 5 7 8
C Code of Selection Sort
void selectionSort(int list[], int size) {
int outer, inner, min; for (outer = 0; outer < size-1; outer++)
{ // outer counts down min = outer; for (inner = outer + 1; inner < size; inner++)
{ if (list[inner] < list[min])
{ min = inner; } }
// list[min] is least among list[outer]..list[list.length - 1] int temp = list[outer]; list[outer] = list[min]; list[min] = temp; }
}
7 2 8 5 4
C Code of Selection Sort
void selectionSort(int list[], int size) {
int outer, inner, min; for (outer = 0; outer < size-1; outer++)
{ // outer counts down min = outer; for (inner = outer + 1; inner < size; inner++)
{ if (list[inner] < list[min])
{ min = inner; } }
// list[min] is least among list[outer]..list[list.length - 1] int temp = list[outer]; list[outer] = list[min]; list[min] = temp; }
}
7 2 8 5 4
outer = 0min = 0
C Code of Selection Sort
void selectionSort(int list[], int size) {
int outer, inner, min; for (outer = 0; outer < size-1; outer++)
{ // outer counts down min = outer; for (inner = outer + 1; inner < size; inner++)
{ if (list[inner] < list[min])
{ min = inner; } }
// list[min] is least among list[outer]..list[list.length - 1] int temp = list[outer]; list[outer] = list[min]; list[min] = temp; }
}
7 2 8 5 4
outer = 0min = 0
inner = 1
C Code of Selection Sort
void selectionSort(int list[], int size) {
int outer, inner, min; for (outer = 0; outer < size-1; outer++)
{ // outer counts down min = outer; for (inner = outer + 1; inner < size; inner++)
{ if (list[inner] < list[min])
{ min = inner; } }
// list[min] is least among list[outer]..list[list.length - 1] int temp = list[outer]; list[outer] = list[min]; list[min] = temp; }
}
7 2 8 5 4
outer = 0min = 0
inner = 1
list [inner] = 2
list [min] = 7
C Code of Selection Sort
void selectionSort(int list[], int size) {
int outer, inner, min; for (outer = 0; outer < size-1; outer++)
{ // outer counts down min = outer; for (inner = outer + 1; inner < size; inner++)
{ if (list[inner] < list[min])
{ min = inner; } }
// list[min] is least among list[outer]..list[list.length - 1] int temp = list[outer]; list[outer] = list[min]; list[min] = temp; }
}
7 2 8 5 4
outer = 0min = 1
inner = 1
list [inner] = 2
list [min] = 7
C Code of Selection Sort
void selectionSort(int list[], int size) {
int outer, inner, min; for (outer = 0; outer < size-1; outer++)
{ // outer counts down min = outer; for (inner = outer + 1; inner < size; inner++)
{ if (list[inner] < list[min])
{ min = inner; } }
// list[min] is least among list[outer]..list[list.length - 1] int temp = list[outer]; list[outer] = list[min]; list[min] = temp; }
}
7 2 8 5 4
outer = 0min = 1
inner = 2
list [inner] = 2
list [min] = 7
C Code of Selection Sort
void selectionSort(int list[], int size) {
int outer, inner, min; for (outer = 0; outer < size-1; outer++)
{ // outer counts down min = outer; for (inner = outer + 1; inner < size; inner++)
{ if (list[inner] < list[min])
{ min = inner; } }
// list[min] is least among list[outer]..list[list.length - 1] int temp = list[outer]; list[outer] = list[min]; list[min] = temp; }
}
7 2 8 5 4
outer = 0min = 1
inner = 2
list [inner] = 8
list [min] = 2
C Code of Selection Sort
void selectionSort(int list[], int size) {
int outer, inner, min; for (outer = 0; outer < size-1; outer++)
{ // outer counts down min = outer; for (inner = outer + 1; inner < size; inner++)
{ if (list[inner] < list[min])
{ min = inner; } }
// list[min] is least among list[outer]..list[list.length - 1] int temp = list[outer]; list[outer] = list[min]; list[min] = temp; }
}
7 2 8 5 4
outer = 0min = 1
inner = 3
list [inner] = 8
list [min] = 2
C Code of Selection Sort
void selectionSort(int list[], int size) {
int outer, inner, min; for (outer = 0; outer < size-1; outer++)
{ // outer counts down min = outer; for (inner = outer + 1; inner < size; inner++)
{ if (list[inner] < list[min])
{ min = inner; } }
// list[min] is least among list[outer]..list[list.length - 1] int temp = list[outer]; list[outer] = list[min]; list[min] = temp; }
}
7 2 8 5 4
outer = 0min = 1
inner = 3
list [inner] = 5
list [min] = 2
C Code of Selection Sort
void selectionSort(int list[], int size) {
int outer, inner, min; for (outer = 0; outer < size-1; outer++)
{ // outer counts down min = outer; for (inner = outer + 1; inner < size; inner++)
{ if (list[inner] < list[min])
{ min = inner; } }
// list[min] is least among list[outer]..list[list.length - 1] int temp = list[outer]; list[outer] = list[min]; list[min] = temp; }
}
7 2 8 5 4
outer = 0min = 1
inner = 4
list [inner] = 5
list [min] = 2
C Code of Selection Sort
void selectionSort(int list[], int size) {
int outer, inner, min; for (outer = 0; outer < size-1; outer++)
{ // outer counts down min = outer; for (inner = outer + 1; inner < size; inner++)
{ if (list[inner] < list[min])
{ min = inner; } }
// list[min] is least among list[outer]..list[list.length - 1] int temp = list[outer]; list[outer] = list[min]; list[min] = temp; }
}
7 2 8 5 4
outer = 0min = 1
inner = 4
list [inner] = 4
list [min] = 2
C Code of Selection Sort
void selectionSort(int list[], int size) {
int outer, inner, min; for (outer = 0; outer < size-1; outer++)
{ // outer counts down min = outer; for (inner = outer + 1; inner < size; inner++)
{ if (list[inner] < list[min])
{ min = inner; } }
// list[min] is least among list[outer]..list[list.length - 1] int temp = list[outer]; list[outer] = list[min]; list[min] = temp; }
}
2 7 8 5 4
outer = 0min = 1
inner = 4
list [inner] = 4
list [min] = 2
C Code of Selection Sort
void selectionSort(int list[], int size) {
int outer, inner, min; for (outer = 0; outer < size-1; outer++)
{ // outer counts down min = outer; for (inner = outer + 1; inner < size; inner++)
{ if (list[inner] < list[min])
{ min = inner; } }
// list[min] is least among list[outer]..list[list.length - 1] int temp = list[outer]; list[outer] = list[min]; list[min] = temp; }
}
2 7 8 5 4
outer = 1min = 1
C Code of Selection Sort
void selectionSort(int list[], int size) {
int outer, inner, min; for (outer = 0; outer < size-1; outer++)
{ // outer counts down min = outer; for (inner = outer + 1; inner < size; inner++)
{ if (list[inner] < list[min])
{ min = inner; } }
// list[min] is least among list[outer]..list[list.length - 1] int temp = list[outer]; list[outer] = list[min]; list[min] = temp; }
}
2 7 8 5 4
outer = 1min = 1
inner = 2
C Code of Selection Sort
void selectionSort(int list[], int size) {
int outer, inner, min; for (outer = 0; outer < size-1; outer++)
{ // outer counts down min = outer; for (inner = outer + 1; inner < size; inner++)
{ if (list[inner] < list[min])
{ min = inner; } }
// list[min] is least among list[outer]..list[list.length - 1] int temp = list[outer]; list[outer] = list[min]; list[min] = temp; }
}
2 7 8 5 4
outer = 1min = 1
inner = 2
list [inner] = 8
list [min] = 7
C Code of Selection Sort
void selectionSort(int list[], int size) {
int outer, inner, min; for (outer = 0; outer < size-1; outer++)
{ // outer counts down min = outer; for (inner = outer + 1; inner < size; inner++)
{ if (list[inner] < list[min])
{ min = inner; } }
// list[min] is least among list[outer]..list[list.length - 1] int temp = list[outer]; list[outer] = list[min]; list[min] = temp; }
}
2 7 8 5 4
outer = 1min = 1
inner = 3
list [inner] = 8
list [min] = 7
C Code of Selection Sort
void selectionSort(int list[], int size) {
int outer, inner, min; for (outer = 0; outer < size-1; outer++)
{ // outer counts down min = outer; for (inner = outer + 1; inner < size; inner++)
{ if (list[inner] < list[min])
{ min = inner; } }
// list[min] is least among list[outer]..list[list.length - 1] int temp = list[outer]; list[outer] = list[min]; list[min] = temp; }
}
2 7 8 5 4
outer = 1min = 1
inner = 3
list [inner] = 5
list [min] = 7
C Code of Selection Sort
void selectionSort(int list[], int size) {
int outer, inner, min; for (outer = 0; outer < size-1; outer++)
{ // outer counts down min = outer; for (inner = outer + 1; inner < size; inner++)
{ if (list[inner] < list[min])
{ min = inner; } }
// list[min] is least among list[outer]..list[list.length - 1] int temp = list[outer]; list[outer] = list[min]; list[min] = temp; }
}
2 7 8 5 4
outer = 1min = 3
inner = 3
list [inner] = 5
list [min] = 5
C Code of Selection Sort
void selectionSort(int list[], int size) {
int outer, inner, min; for (outer = 0; outer < size-1; outer++)
{ // outer counts down min = outer; for (inner = outer + 1; inner < size; inner++)
{ if (list[inner] < list[min])
{ min = inner; } }
// list[min] is least among list[outer]..list[list.length - 1] int temp = list[outer]; list[outer] = list[min]; list[min] = temp; }
}
2 7 8 5 4
outer = 1min = 3
inner = 4
list [inner] = 5
list [min] = 5
C Code of Selection Sort
void selectionSort(int list[], int size) {
int outer, inner, min; for (outer = 0; outer < size-1; outer++)
{ // outer counts down min = outer; for (inner = outer + 1; inner < size; inner++)
{ if (list[inner] < list[min])
{ min = inner; } }
// list[min] is least among list[outer]..list[list.length - 1] int temp = list[outer]; list[outer] = list[min]; list[min] = temp; }
}
2 7 8 5 4
outer = 1min = 3
inner = 4
list [inner] = 4
list [min] = 5
C Code of Selection Sort
void selectionSort(int list[], int size) {
int outer, inner, min; for (outer = 0; outer < size-1; outer++)
{ // outer counts down min = outer; for (inner = outer + 1; inner < size; inner++)
{ if (list[inner] < list[min])
{ min = inner; } }
// list[min] is least among list[outer]..list[list.length - 1] int temp = list[outer]; list[outer] = list[min]; list[min] = temp; }
}
2 7 8 5 4
outer = 1min = 4
inner = 4
list [inner] = 4
list [min] = 4
C Code of Selection Sort
void selectionSort(int list[], int size) {
int outer, inner, min; for (outer = 0; outer < size-1; outer++)
{ // outer counts down min = outer; for (inner = outer + 1; inner < size; inner++)
{ if (list[inner] < list[min])
{ min = inner; } }
// list[min] is least among list[outer]..list[list.length - 1] int temp = list[outer]; list[outer] = list[min]; list[min] = temp; }
}
2 4 8 5 7
outer = 1min = 4
inner = 4
list [inner] = 4
list [min] = 4
C Code of Selection Sort
void selectionSort(int list[], int size) {
int outer, inner, min; for (outer = 0; outer < size-1; outer++)
{ // outer counts down min = outer; for (inner = outer + 1; inner < size; inner++)
{ if (list[inner] < list[min])
{ min = inner; } }
// list[min] is least among list[outer]..list[list.length - 1] int temp = list[outer]; list[outer] = list[min]; list[min] = temp; }
}
2 4 8 5 7
outer = 2min = 2