算法导论第二章算法入门2.1 插入排序

插入排序

// insertion_sort.h not with template
#include <iostream>
#include <stdint.h>
// INSERTION-SORT(A)
// for j = 2 to A.length
//     key = A[j]
//     // Insert A[j] into sorted sequence A[1..j - 1].
//     i = j - 1
//     while i > 0 and a[i] > key
//         a[i + 1] = a[i]
//         i = i - 1
//     a[i + 1] = key

// allow the same key

void insertion_sort(uint64_t* A, uint64_t const n)
{   
    uint64_t key;
    int64_t i;
    // j = 2 to A.length(j 1 to n - 1)
    for (uint64_t j = 1; j < n; j++) // j begin with A[1]
    {
        key = A[j];
        i = j - 1;                   // i begin with A[0]
        while (i >= 0 && A[i] > key)
        {
            A[i + 1] = A[i];
            i--;
        }
        A[i + 1] = key;
    }
}

// insertion_sort.cpp
#include "insertion_sort.h"

#ifdef __linux
#include <stdio.h>
#endif

int main()
{
    uint64_t array[6] = { 5, 2, 4, 6, 1, 3 };
    for (uint64_t i = 0; i < sizeof(array) / sizeof(uint64_t); i++)
    {
        std::cout << array[i] << " ";
    }
    std::cout << std::endl;
    insertion_sort(array, sizeof(array) / sizeof(uint64_t));
    for (uint64_t i = 0; i < sizeof(array) / sizeof(uint64_t); i++)
    {
        std::cout << array[i] << " ";
    }
    std::cout << std::endl;
    getchar();
    return 0;
}

插入排序模版

// 插入排序 insertion_sort_t.h

#include <iostream>
#include <string>

// INSERTION-SORT(A)
// for j = 2 to A.length
//     key = A[j]
//     // Insert A[j] into sorted sequence A[1..j - 1].
//     i = j - 1
//     while i > 0 and a[i] > key
//         a[i + 1] = a[i]
//         i = i - 1
//     a[i + 1] = key

template <class Type> void insert_sort_t(Type * const a, int const & n)
{
    Type key;
    // j赋值为1因为是从第二个元素开始插入排序
    // j<n因为n代表着待排序的数组元素的个数，n-1为最后一个元素
    for (int j = 1; j < n; j++)
    {
        key = a[j];    // 等待插入的元素为a[j]
        int i = j - 1; // a[0...j-1]为已经有序的部分，a[j+1...n-1]为还没有排序的部分
        // 我们首先要比较的是a[j]与a[j-1]
        while ((i >= 0) && (a[i] > key))
        {
            a[i + 1] = a[i]; // 所有比a[j]大的元素后移一位
            i--;
        }
        a[i + 1] = key;      // 将a[j]放到正确的位置上去
    }
}


// insertion_sort_t.cpp
#include "insertion_sort_t.h"

#ifdef __linux
#include <stdio.h>
#endif

int main()
{
    int a[6] = { 5, 2, 4, 6, 1, 3 };
    insert_sort_t(a, 6);
    for (int i = 0; i < 6; i++)
    {
        std::cout << a[i] << " ";
    }
    std::cout << std::endl;
    std::string b[4] = { "hello", "China", "haha",  "I Love China"};
    insert_sort_t(b, 4);
    for (int i = 0; i < 4; i++)
    {
        std::cout << b[i] << " ";
    }
    std::cout << std::endl;
    getchar();
    return 0;
}