Sorting Algorithms Visualization | Selection Sort - GeeksforGeeks

09 Sep, 2019
Pre-requisite: Selection Sort
The human brain can easily process visuals in spite of long codes to understand the algorithms. In this article, Selection Sort visualization has been implemented using graphics.h library. As we all know selection sort first finds the minimum element from the unsorted array and swaps it with the first element of the unsorted array in each pass. It becomes difficult to analyze the data manually between two algorithms or vice versa, but plotting graphically it is much easier to understand.
Approach:
The white line is used to represent the length of number (9 being represented by 9 pixels vertically upwards) while its position represents its index in the array.
Graphical representation of randomly distributed numbers is shown below.
Graphically sorting can be shown by first coloring the minimum element from unsorted array as green color.
Now swap it with the first element of unsorted array and also swap the color for those two number as shown in code by swap_colors() function.
Here delay() can be increased to see the transition in the graph.
Examples:
Pre-defined Functions Used:
setcurrentwindow(): A function which is used to set the size of current window.
setcolor(n): A function which is used to change the color of cursor by changing the value of n.
delay(n): A function which is used to delay the program by n milliseconds. It is being used for slowing down the transitions speed
line(x1, y1, x2, y2): A function which is used to draw an line from point (x1, y1) to point (x2, y2). (0, 0) being the left top corner of the screen and bottom right be (n1, n2) where n1, n2 are the width and height of the current window. There are other graphics which can be applied to this line using setcolor().
Below is the program to visualize the Selection Sort algorithm:
// C++ program for visualization// of bubble sort  #include "graphics.h"#include <bits/stdc++.h>  using namespace std;  // Initialize the size// with the total numbers to sorted// and the gap to be maintained in graphvector<int> numbers;int size = 200;int gap = 4;  // Function for swapping the lines graphicallyvoid swap_colors(int i, int j, int x, int y){      // y is the minimum element,    // first make this number green    // Now, swapping it by making black again    // and then draw the pixels    // for white colour with x value.    setcolor(GREEN);    line(j, size, j, size - y);      delay(500);      setcolor(BLACK);    line(j, size, j, size - y);      setcolor(WHITE);    line(j, size, j, size - x);      // X is the element to be swapped,    // first make this number black    // Now, highlight y with green    // representing the minimum element    // and then draw the pixels    // for white colour with y value.    setcolor(BLACK);    line(i, size, i, size - x);      setcolor(GREEN);    line(i, size, i, size - y);      delay(500);      setcolor(WHITE);    line(i, size, i, size - y);}  // Function for swapping two numbersvoid swap(int* xp, int* yp){    int temp = *xp;    *xp = *yp;    *yp = temp;}  // Selection sort functionvoid selsort(){    for (int i = 0; i < size - 1; i++) {          // Find the minimum element        // in unsorted array        int min_idx = i;          for (int j = i + 1; j < size; j++) {            if (numbers[j] < numbers[min_idx]) {                min_idx = j;            }        }          // Swap the found minimum element        // with the first element        // delay(500);        swap(&numbers[min_idx],             &numbers[i]);          // Function to show transition in swapping        swap_colors(gap * i + 1,                    gap * (min_idx) + 1,                    numbers[min_idx],                    numbers[i]);    }}  // Driver programint main(){      // auto detection of screen size    int gd = DETECT, gm;    int wid1;      // Graph initialization    initgraph(&gd, &gm, NULL);      // setting up window size (gap*size) * (size)    wid1 = initwindow(gap * size + 1, size + 1);    setcurrentwindow(wid1);      // Initializing the array    for (int i = 1; i <= size; i++)        numbers.push_back(i);      // Find a seed and shuffle the array    // to make it random.    // Here  different type of array    // can be taken to results    // such as nearly sorted, already sorted,    // reverse sorted to visualize the result    unsigned seed        = chrono::system_clock::now()              .time_since_epoch()              .count();      shuffle(numbers.begin(),            numbers.end(),            default_random_engine(seed));      // Initial plot of numbers in graph taking    // the vector position as x-axis and its    // corresponding value will be the height of line.    for (int i = 1; i <= gap * size; i += gap) {        line(i, size, i, (size - numbers[i / gap]));    }      // Delay the code    delay(200);      // Call sort    selSort();      for (int i = 0; i < size; i++) {        cout << numbers[i] << " ";    }    cout << endl;      // Wait for sometime .    delay(5000);      // Close the graph    closegraph();      return 0;}
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Visualization:
Input Visualization:Unsorted Array
Unsorted Array
Output Visualization:Sorting the array using Selection Sort
Sorting the array using Selection Sort
selection-sort
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