C++ 排序

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sort使用

// alg_sort.cpp// compile with: /EHsc#include <vector>#include <algorithm>  //sort必须#include <functional>      // For greater<int>( )#include <iostream>// Return whether first element is greater than the secondbool UDgreater ( int elem1, int elem2 ){return elem1 > elem2;//降序}int main( ){using namespace std;vector <int> v1;vector <int>::iterator Iter1;int i;for ( i = 0 ; i <= 5 ; i++ ){v1.push_back( 2 * i );}int ii;for ( ii = 0 ; ii <= 5 ; ii++ ){v1.push_back( 2 * ii + 1 );}cout << "Original vector v1 = ( " ;for ( Iter1 = v1.begin( ) ; Iter1 != v1.end( ) ; Iter1++ )cout << *Iter1 << " ";cout << ")" << endl;sort( v1.begin( ), v1.end( ) );cout << "Sorted vector v1 = ( " ;for ( Iter1 = v1.begin( ) ; Iter1 != v1.end( ) ; Iter1++ )cout << *Iter1 << " ";cout << ")" << endl;// To sort in descending order. specify binary predicatesort( v1.begin( ), v1.end( ), greater<int>( ) );cout << "Resorted (greater) vector v1 = ( " ;for ( Iter1 = v1.begin( ) ; Iter1 != v1.end( ) ; Iter1++ )cout << *Iter1 << " ";cout << ")" << endl;// A user-defined (UD) binary predicate can also be usedsort( v1.begin( ), v1.end( ), UDgreater );cout << "Resorted (UDgreater) vector v1 = ( " ;for ( Iter1 = v1.begin( ) ; Iter1 != v1.end( ) ; Iter1++ )cout << *Iter1 << " ";cout << ")" << endl;}

内部排序:插入选择交换

1.插入排序用直接插入排序法//从小到大//直接插入排序函数模板template<class T>void insertionSort(T arr[],int n){for(int i=0;i<n;i++){//从a[i - 1]开始向a[0]方向扫描各元素,寻找适当位置插入arr[i]T tem=arr[i];int j=i;while (j>0 && tem<arr[j-1])//tem进行比较{arr[j]=arr[j-1];j--;}arr[j]=tem;}}2.选择排序直接选择排序每次从待排序序列中选择一个关键字最小的元素，（当需要按关键字升序排列时），顺序排在已排序序列的最后，直至全部排完。//从小到大void mySwap(T &a,T &b){T tem;tem=a;a=b;b=tem;}template<class T>void selectionSort(T arr[],int n){for (int i=0;i<n-1;i++){int leastIndex = i;//最小元素之下标初值设为ifor (int j=i+1;j<n;j++){if (arr[j]<arr[leastIndex]){leastIndex=j;}}mySwap(arr[i],arr[leastIndex]);}}3.交换排序 冒泡排序发生交换的位置必定小于n，且这个位置之后的数据必定已经有序了，记录下这位置template<class T>void mySwap(T &a,T &b){T tem;tem=a;a=b;b=tem;}template<class T>void bubbleSort(T arr[],int n){//发生交换的位置必定小于n，且这个位置之后的数据必定已经有序了，记录下这位置int i=n-1;while (i>0){int lastExchangeIndex = 0;//必须每次都初始化为0for (int j=0;j<i;j++){if (arr[j+1]<arr[j]){mySwap(arr[j+1],arr[j]);lastExchangeIndex=j;}}i=lastExchangeIndex;}}

查找: 顺序查找折半查找

4.顺序查找//顺序查找函数模板template <class T>int SeqSearch(T list[],int n,T key){for(int i=0;i < n;i++)if (list[i] == key)return i;return -1;}5.折半查找template<class T>int  binSearch(const T list[], int n, const T &key){int low=0,high=n-1;while (low<=high)//必须是<=号{int mid=(low+high)/2;if (key==list[mid])//是和list[mid] 进行的操作    return mid;else if (key<list[mid])high=mid-1;elselow=mid+1;}return -1;}

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