O(n2)的冒泡,选择,插入,先不贴,先贴归并,快排,堆排,
O(nlog(n))
归并排序
二路归并递归写法:时间O(nlog(n)),稳定,总时间O(nlog),空间:O(n+log(n)),n为内存,log(n)为栈空间
#include<bits/stdc++.h> using namespace std; //归并过程 void merge(int arr[], int l, int mid, int r){ int len=r-l+1;//合并长度 vector<int> help; //临时数组 int lindex = l; int rindex = mid+1; while(lindex<=mid && rindex<=r){ if(arr[lindex]<arr[rindex]){ help.push_back(arr[lindex++]); }else{ help.push_back(arr[rindex++]); } } while(lindex<=mid){ help.push_back(arr[lindex++]); } while(rindex<=r){ help.push_back(arr[rindex++]); } for(int i=0;i<len;i++){ arr[l+i]=help[i]; } } void mergesort(int arr[], int l,int r){ if(l==r) return; int mid=(r+l)/2; mergesort(arr,l,mid); mergesort(arr,mid+1,r); merge(arr,l,mid,r); } int main(){ int n; while(cin >> n){ int arr[n]; for(int i = 0; i < n; i++) cin>>arr[i]; mergesort(arr, 0,n-1);//排序数组,和起始终止de下标 for(int i = 0; i < n; i++){ cout << arr[i] << " "; } cout << endl; } return 0; } /* 10 8 6 7 9 2 3 4 1 0 5 */
非递归和多路归并再说:
堆排序:对数组进行下标从1开始的堆排序,不稳定,O(nlogn)时间,O(1)空间
#include<bits/stdc++.h> using namespace std; void heapadjust(int arr[],int index,int len){ int temp=arr[index]; for(int i=2*index;i<=len;i*=2){ if(i<len && arr[i]<arr[i+1]) i++; if(temp>arr[i]) break; arr[index]=arr[i]; index=i; } arr[index]=temp; } void heapsort(int arr[],int len){ //从最后一个非叶节点建立堆,从下标为1处开始排序 for(int i=len/2;i>=1;i--){ heapadjust(arr,i,len); } for(int i=len;i>1;i--){ swap(arr[1],arr[i]); heapadjust(arr,1,i-1); } } int main(){ int n; while(cin >> n){ int arr[n];vector<int> nums;arr[0]=0; for(int i = 1; i <= n; i++) {cin>>arr[i];nums.push_back(arr[i]);} heapsort(arr,n); for(int i = 1; i <= n; i++){ cout << arr[i] << " "; } cout << endl; } return 0; } /* 10 8 6 7 9 2 3 4 1 0 5 */
快速排序
递归实现:不稳定,最坏O(n2),空间复杂度(由递归深度决定,O(n)~O(logn))
#include <bits/stdc++.h> using namespace std; int partitions(int arr[],int low,int high){ int pivotkey=arr[low]; while(low<high){ while(low<high && arr[high]>=pivotkey) high--; arr[low]=arr[high]; while(low<high && arr[low]<=pivotkey) low++; arr[high]=arr[low]; } arr[low]=pivotkey; return low; } void quicksort(int arr[],int low,int high){ if(low<high){ int pivot=partitions(arr,low,high); quicksort(arr,low,pivot-1); quicksort(arr,pivot+1,high); } } int main(){ int n; while(cin>>n){ int arr[n]; for(int i=0;i<n;i++) cin>>arr[i]; quicksort(arr,0,n-1); for(int i=0;i<n;i++) cout<<arr[i]<<" "; cout<<endl; } } /* 10 8 6 7 9 2 3 4 1 0 5 */