全排列算法-c++实现

#include <iostream>
#include <algorithm>
using namespace std;
int main(){
    int arr[4]={1,2,3,4};
    do{
        for(int i = 0; i < 4; i++){
            cout << arr[i] << ‘ ‘;
        }
        cout << endl;
    }while(next_permutation(arr,arr+4));
    cout << "final state:" <<endl;
    for(int i = 0; i < 4; i++){
        cout << arr[i] << ‘ ‘;
    }
    cout << endl;
    return 0;
}

#include <iostream>
using namespace std;
template <class T>
void Swap(T &a,T &b){
    T temp = a;
    a = b;
    b = temp;
}
template <class T>
void Swap(T list[],int i,int k){
    T list_i = list[i];
    if(i < k){
        for(int j = i; j < k; j++){
            list[j]= list[j+1];
        }
    }
    else if(i > k){
        for(int j = i; j>k; j--){
            list[j]= list [j-1];
        }
    }
    list[k] = list_i;
}
template <class T>
void Perm(T list[],int k,int m){
    if(k == m){
        for(int i = 0; i <= m; i++){
            cout << list[i] << ‘ ‘;
        }
        cout << endl;
    }
    else{
        for(int i = k; i <= m; i++){
            Swap(list, i, k);
            Perm(list, k+1, m);
            Swap(list, k, i);
        }
    }
    return;
}
int main(){
    int a[6]={1,2,3,4,5,6};
    Perm(a,0,3);
    return 0;
}

#include <iostream>
using namespace std;
template <class T>
void Swap(T &a,T &b){
    T temp = a;
    a = b;
    b = temp;
}
template <class T>
void Reverse(T list[], int i, int k){       //转置 
    T *listcpy = new T[k + 1];
    for(int j = i; j <= k; j++){
        listcpy[j] = list[i + k - j];
    }
    for(int j = i; j <= k; j++){
        list[j] = listcpy[j];
    }
    delete listcpy;
}
template <class T>
int Upper_Bound(T list[], int l, int r, T item){ //二分查找降序序列(l,r)中 
    int mid = (l + r + 1) / 2;                   //第一个大于item的位置 
    while(l < r){
        mid = (l + r + 1) / 2;
        if(list[mid] < item){
            r = mid - 1;
        }
        else{
            l = mid;
        }
    }
    return l;
}
template <class T>
bool Next_Permutation(T list[], int i, int k){
    int n = -1, m = 0, t = k;
    while(n == -1 && t != i){
        if(list[t] > list[t-1]){   //n的位置 
            n = t - 1;
        }
        t--;
    }
    if(n == -1){                   //降序 
        Reverse(list, i, k);
        return false;
    }
    else{
        m = Upper_Bound(list, n+1, k, list[n]);   //m的位置 
        Swap(list[n], list[m]);       //交换n,m上的值 
        Reverse(list, n+1, k);        //倒置从n+1到k 
        return true;
    }
}
int main(){
    int arr[4]={1,2,3,4};
    do{
        for(int i = 0; i < 4; i++){
            cout << arr[i] << ‘ ‘;
        }
        cout << endl;
    }while(Next_Permutation(arr, 0, 3));
    cout << "final state:" <<endl;
    for(int i = 0; i < 4; i++){
        cout << arr[i] << ‘ ‘;
    }
    cout << endl;
    return 0;
}