常见排序代码（C语言）

Posted 2023-01-22 huatian5

选快希堆不稳（是不稳定的排序），
堆归选基不变（运行时间不发生变化，与初始状态无关）

插入排序

/**
 * Note: The returned array must be malloced, assume caller calls free().
 */
int* sortArray(int* nums, int numsSize, int* returnSize)
    for (int i = 1, j; i < numsSize; i++) 
        int temp = nums[i];
        for (j = i - 1; j >= 0 && temp < nums[j]; j--) 
            nums[j+1] = nums[j];
        
        nums[j+1] = temp;
    
    *returnSize = numsSize;
    return nums;

选择排序

/**
 * Note: The returned array must be malloced, assume caller calls free().
 */
int* sortArray(int* nums, int numsSize, int* returnSize)
    for (int i = 0, j; i < numsSize; i++) 
        int min_pos = i;
        for (int j = i+1; j < numsSize; j++) 
            if (nums[j] < nums[min_pos]) 
                min_pos = j;
            
        
        int temp = nums[i];
        nums[i] = nums[min_pos];
        nums[min_pos] = temp;
    
    *returnSize = numsSize;
    return nums;

冒泡排序（优化可在第一层循环内检查是否发生交换，所以运行时间与初始状态有关）

/**
 * Note: The returned array must be malloced, assume caller calls free().
 */
int* sortArray(int* nums, int numsSize, int* returnSize)
    for (int i = 0, j; i < numsSize; i++) 
        for (int j = 0; j < numsSize - 1 - i; j++) 
            if (nums[j] > nums[j+1]) 
                int temp = nums[j];
                nums[j] = nums[j+1];
                nums[j+1] = temp;
            
        
    
    *returnSize = numsSize;
    return nums;

希尔排序

基数排序

快速排序

最理想时间复杂度O(nlogn)，最坏时间复杂度O(n^2)，实际应用中，快速排序的平均时间复杂度为O(nlogn)

#include<iostream>
#include<algorithm>
using namespace std;

int a[105] = 3,5,7,9,2,68,48,6,59,18;
void quicksort(int left,int right)

    if(left > right)//递归终止条件
        return;
    int i = left;
    int j = right;
    while(i < j)
    
        while(i < j && a[j] >= a[left])
            j--;
        while(i < j && a[i] <= a[left])
            i++;
        if(i < j)
            swap(a[i],a[j]);
    
    swap(a[left],a[i]);//基准归位
    quicksort(left,i-1);
    quicksort(i+1,right);

int main()

    quicksort(0,9);
    for(int i = 0;i < 10;i++)
        cout<<a[i]<<endl;

寻找第k小元素

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <utility>
#include <vector>
using namespace std;

int a[105] = 3,5,7,9,2,68,48,6,59,18;

int findkth(int l,int r,int k)

    if(l > r)
        return -1;
    int i = l, j = r;
    while(i < j)
    
        while(i < j && a[j] >= a[l])
            j--;
        while(i < j && a[i] <= a[l])
            i++;
        if(i < j)
            swap(a[i],a[j]);
    
    swap(a[i],a[l]);
    if(i == k-1)
        return a[i];
    else if(i > k-1)
        return findkth(l,i-1,k);
    else
        return findkth(i+1,r,k);

int main()

    printf("%d\\n",findkth(0,6,3));

归并排序

时间复杂度O(nlogn)

#include<iostream>
#include<algorithm>
using namespace std;


int a[105] = 3,5,7,9,2,68,48,6,59,18,b[105];
void mergesort(int *a,int left,int right,int *T)

    if(right - left > 1)
    
        int mid = left + (right-left) / 2;
        int i = left,j = mid,k = left;
        mergesort(a,left,mid,T);
        mergesort(a,mid,right,T);
        while(i < mid || j < right)
        
            if(j >= right || (i < mid && a[i] <= a[j]))
                T[k++] = a[i++];
            else
                T[k++] = a[j++];
        
        for(int i = left;i < right;i++)
            a[i] = T[i];
    

int main()

    mergesort(a,0,10,b);
    for(int i = 0;i < 10;i++)
        cout<<a[i]<<endl;

#include<iostream>
#include<algorithm>
using namespace std;

int a[105] = 3,5,7,9,2,68,48,6,59,18,b[105];
void mergesort(int *a,int left,int right,int *T)

    if(left >= right)
        return;
    int mid = left + (right-left) / 2;
    int i = left,j = mid+1,k = left;
    mergesort(a,left,mid,T);
    mergesort(a,mid+1,right,T);
    while(i <= mid && j <= right)
    
        if(a[i] <= a[j])
            T[k++] = a[i++];
        else
            T[k++] = a[j++];
    
    while(i <= mid) T[k++] = a[i++];
    while(j <= right) T[k++] = a[j++];
    for(int i = left;i <= right;i++)
        a[i] = T[i];

int main()

    mergesort(a,0,9,b);
    for(int i = 0;i < 10;i++)
        cout<<a[i]<<endl;

堆排序

#include<bits/stdc++.h>

using namespace std;
int a[105] = 3,5,7,9,2,68,48,6,59,18;
void adjust(int len,int index)

    int left = index*2+1;
    int right = index*2+2;
    int maxn = index;//最大数的下标
    if(left < len && a[left] > a[maxn])
        maxn = left;
    if(right < len && a[right] > a[maxn])
        maxn = right;
    if(maxn != index)//有更新
    
        swap(a[maxn],a[index]);
        adjust(len,maxn);
    

void heap_sort(int n)//最大堆

    for(int i = n/2 - 1;i >= 0;i--)//对每一个非也叶节点进行堆调整
        adjust(n,i);
    for(int i = n-1;i >= 1;i--)
    
        swap(a[0],a[i]);//将当前最大的放到数组末尾
        adjust(i,0);//对未排序的部分继续堆排序
    


int main()

    heap_sort(10);
    for(int i = 0;i < 10;i++)
        cout<<a[i]<<endl;