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next_permutation()

在標頭檔案<algorithm>裡面有如下程式碼：

int a[];
do
{

}
while(next_permutation(a,a+n));

例子：

#include<bits/stdc++.h>
#include<set>
#include<vector>
#include<deque>
#include<map>
#include<queue>
using namespace std;
int main(){
    int n;
    cin
 
>>n;
    int * p = new int[n];
    for (int i = 0; i < n; i++)
    {
        cin>>p[i];
    }
    sort(p,p+n);
    do
    {
        for (int i = 0; i < n; i++)
        {
            cout<<p[i]<<" ";
        }
        cout<<endl;        
    } while (next_permutation(p,p+n));

    cout
 
<<endl;
    string s = "aba";
    sort(s.begin(), s.end());
    do {
        cout << s << '\n';
    } while(next_permutation(s.begin(), s.end()));


}

輸出：

3
1 2 3
1 2 3
1 3 2
2 1 3
2 3 1
3 1 2
3 2 1

aab
aba
baa

prev_permutation

例子

#include<bits/stdc++.h>
#include<set
 
>
#include<vector>
#include<deque>
#include<map>
#include<queue>
using namespace std;
int main(){
    int n;
    cin>>n;
    int * p = new int[n];
    for (int i = 0; i < n; i++)
    {
        cin>>p[i];
    }
    sort(p,p+n,greater<int>());
    do
    {
        for (int i = 0; i < n; i++)
        {
            cout<<p[i]<<" ";
        }
        cout<<endl;        
    } while (prev_permutation(p,p+n));

    cout<<endl;
    string s = "aba";
    sort(s.begin(), s.end());
    do {
        cout << s << '\n';
    } while(prev_permutation(s.begin(), s.end()));


}

輸出：

3
1 2 3
3 2 1
3 1 2
2 3 1
2 1 3
1 3 2
1 2 3

aab