Implementing the Selection Sort Algorithm in C++
Selection sort is a simple and intuitive sorting algorithm. Its core idea is to repeatedly select the smallest (or largest) element from the unsorted elements and place it at the end of the sorted sequence until all elements are sorted. The basic steps are as follows: the outer loop controls the current starting position of the unsorted elements; the inner loop finds the minimum value among the remaining elements; the swap operation moves the minimum value to the current starting position; this process repeats until all elements are sorted. Taking the array {64, 25, 12, 22, 11} as an example, the process is demonstrated: when i=0, the minimum value 11 is found and swapped to the first position; when i=1, 12 is found and swapped to the second position; when i=2, 22 is found and swapped to the third position; no swap is needed when i=3, and the array is finally sorted. The C++ code is implemented with two nested loops: the outer loop controls the position i, the inner loop finds the index minIndex of the minimum value, and swaps arr[i] with arr[minIndex]. The time complexity is O(n²) and the space complexity is O(1). Selection sort is easy to implement and requires no additional space. It is suitable for sorting small-scale data and serves as a foundational example for understanding sorting algorithms.
Read MoreBubble, Selection, Insertion Sort: Who is the Entry-Level 'Sorting King'?
This article introduces the significance of sorting and three basic sorting algorithms. Sorting is a fundamental operation that rearranges data according to rules to achieve a more ordered state, and it is a prerequisite for understanding complex algorithms. The core ideas and characteristics of the three algorithms are as follows: Bubble Sort repeatedly "bubbles" the largest number to the end through multiple passes, with an intuitive logic but frequent swaps, having a time complexity of O(n²). Selection Sort selects the smallest number in each round and inserts it, with fewer swaps but instability, also with O(n²) complexity. Insertion Sort is similar to arranging playing cards, suitable for small-scale or nearly ordered data, and its complexity is close to O(n). Although these three algorithms are simple, they form the foundation of more complex sorts (such as Heap Sort and Merge Sort). For beginners, it is more important to grasp the core ideas of "selecting the smallest, inserting appropriately, and bubbling the largest," and to understand the thinking of "gradually building an ordered sequence," rather than getting caught up in efficiency. This is the key to understanding the essence of sorting.
Read MoreHow Sorting Algorithms Implement Ascending/Descending Order? A Guide for Data "Obedience"
This article introduces methods for sorting algorithms to implement data in ascending/descending order, with the core being to make data "obey" through algorithmic rules. The significance of sorting: arranging messy data in ascending order (from small to large) or descending order (from large to small), such as organizing playing cards. Three basic algorithm implementation rules: 1. **Bubble Sort**: When ascending, large numbers "bubble" and move backward (swap if front > back); when descending, small numbers "sink" and move backward (swap if front < back), like bubbles rising/falling. 2. **Selection Sort**: When ascending, select the smallest number in each round and place it on the left; when descending, select the largest number and place it on the left, similar to selecting class monitors to take their positions in order. 3. **Insertion Sort**: When ascending, insert the new number into the correct position in the already sorted part (from left to right, increasing); similarly for descending (from left to right, decreasing), like inserting playing cards into a sorted sequence. Core logic: Adjust the comparison rule (> or <) to determine the data movement direction. Ascending/descending order essentially involves "making data move according to the rules". It is recommended to first master basic algorithms and manually simulate data movement to understand the logic.
Read MoreSelection Sort: One of the Simplest Sorting Algorithms with the Least Swaps Implementation Method
Selection Sort is a fundamental sorting algorithm in computer science. Due to its simple logic and the minimum number of swaps, it is the first choice for beginners to get started. The core idea of Selection Sort is to divide the array into two parts: sorted and unsorted. In each iteration, the smallest element in the unsorted part is found and swapped with the first element of the unsorted part, gradually expanding the sorted part until the entire array is sorted. For example, for the array [64, 25, 12, 22, 11], through multiple rounds of finding the minimum element and swapping (such as swapping 11 to the first position in the first round and 12 to the second position in the second round), an ascending order can be achieved. Selection Sort involves the minimum number of swaps (at most n-1 swaps). Its time complexity is O(n²) (for all best, worst, and average cases), while the space complexity is only O(1). Its advantages include simplicity, low swap cost, and minimal space requirements. However, its drawbacks are low time efficiency and being an unstable sort (the relative order of equal elements may change). It is suitable for sorting small-scale data or scenarios where swap count is sensitive (e.g., embedded systems). Mastering Selection Sort helps in understanding the core ideas of sorting and laying a foundation for learning more complex algorithms.
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