Chapter 2-InsertionSort

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插入排序(Insertion Sort)的基本思想是：每次将一个待排序的元素，按其大小插入到前面已经排好序的子序列中的适当位置，直到全部元素插入完成为止。
设数组为a[0…n-1]。
1.初始时，a[0]自成1个有序区，无序区为a[1..n-1]。令i=1。
2.将a[i]并入当前的有序区a[0…i-1]中形成a[0…i]的有序区间。
3.i++并重复第二步直到i==n-1。排序完成。

Time Complexity: O(n2)
Space Complexity: O(1)
InsertionSort.cc

#include<iostream>using namespace std;template<typename T>void InsertionSort(T sort_array[], int length);int main(){    int test_array1[10] = {9, 8, 7, 6, 5, 4, 3, 2, 1, 0};    int test_array2[9] = {5, 0, -99, 3, 56, 7, 8, -55, 56};    int test_array3[10] = {-1, -8, 50, 4, 20, 0, 45, 9999, 520, 555555};    InsertionSort(test_array1, 10);    InsertionSort(test_array2, 9);    InsertionSort(test_array3, 10);    cout << "test_array1:\n";    for(int index = 0; index < 10; index++)    {        cout << test_array1[index] << " ";    }    cout << "\ntest_array2:\n";    for(int index = 0; index < 9; index++)    {        cout << test_array2[index] << " ";    }    cout << "\ntest_array3:\n";    for(int index = 0; index < 10; index++)    {        cout << test_array3[index] << " ";    }    cout << endl;    return 0;}template<typename T>void InsertionSort(T sort_array[], int length){    // sort_index is the index of element that we want to insert now    // sort_array[0] is automatically sorted, so sort_index begins from 1    for(int sort_index = 1; sort_index < length; sort_index++)    {        // store element in key        T key = sort_array[sort_index];        // compare from end to front only use 1 loop: move elements and        // find proper position to insert key concurrently. Because when we can't move        // elements, we find the proper position.        // Otherwise compare from front to end use 2 loops: find the proper position        // in one loop; and move elements in the other loop.        int compare_index = sort_index - 1;  // compare from end to front        while(compare_index >= 0 && sort_array[compare_index] > key)        // if key is smaller than some elements in the front-sorted-array, then move        {            // we assume sort_array[compare_index + 1] = key before moving            sort_array[compare_index + 1] = sort_array[compare_index];            compare_index--;  // continue        }        // when we can't move elements, we find the proper position to insert key.        sort_array[compare_index + 1] = key;    }}

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