Solution for exercise 1.2-1 in Introduction to Algorithms_假设需要在一个n n 矩阵中搜索一个数字该矩阵每行每列都按升序排列伪代码-优快云博客

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本文介绍了一种简单的排序算法——选择排序。通过伪代码详细展示了该算法的工作原理：每次从未排序的部分找出最小元素并放到已排序部分的末尾。无论最佳还是最坏情况，选择排序的时间复杂度均为θ(n²)。

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Consider sorting n numbers stored in array A by first finding the smallest element of A and putting it in the first entry of another array B. Then find the second smallest element of A and put it in the second entry of B. Continue in this manner for the n elements of A. Write pseudocode for this algorithm, which is known as selection sort. Give the best-case and worst-case running times of selection sort in θ-notation.

/*
* Sorting n numbers stored in array A by finding the smallest element of
* unsorted part, and putting it in the end of sorted part.
*
* The best-case running times in θ-notation is θ(n^2).
* The worst-case running times in θ-notation is θ(n^2).
*/
void Algorithms::selectionSort(int A[], int n) {
    int min;

    for (int i = 0; i < n; i++) {
        min = i;
        for (int j = i + 1; j < n; j++) {
            if (A[j] < A[min]) {
                min = j;
            }
        }

        if (min > i) {
            // switch A[i] and A[min]
            int temp = A[i];
            A[i] = A[min];
            A[min] = temp;

            // Alternative 1 for switching A[i] and A[min]
            // A[i] ^= A[min];
            // A[min] ^= A[i];
            // A[i] ^= A[min];

            // alternative 2 for switching A[i] and A[min]
            // A[i] += A[min];
            // A[min] = A[i] - A[min];
            // A[i] = A[i] - A[min];
        }
    }
}