#include <stdio.h>
int n,m;
void dfs(int p,int sum,int state)
{
    if(sum + n - p<m) return; 
    if(sum==m)
    {
        for(int i=0;i<n;i++)
            if(state>>i&1)
                printf("%d ",i+1);
        printf("\n");
        return;
    }
    if(p==n) return;
    dfs(p+1,sum+1,state|1<<p);
    dfs(p+1,sum,state);
}
int main()
{
    scanf("%d%d",&n,&m);
    dfs(0,0,0);
}

#include <bits/stdc++.h> using namespace std;

int n, m; int res[1234567];

void print () { for (int i = 1; i <= m; i++) { cout << res[i] << " "; } cout << endl; }

void dfs (int cur) { if (cur > m) { print (); return ; } for (int i = res[cur - 1] + 1; i <= n; i++) { res[cur] = i; dfs (cur + 1); } }

int main() { cin >> n >> m; dfs (1); return 0; }

纯分享

#include <queue>
#include <math.h>
#include <stack>
#include <stdio.h>
#include <iostream>
#include <vector>
#include <iomanip>
#include <string.h>
#include <algorithm>
using namespace std;
#define LL long long
const int N = 1e5 + 10;
const int INF = 0x3f3f3f3f;
int a[N];
int n ,m;
void f(int last , int step)
{
	if(step == m)
	{
		for(int i = 0 ; i < step ; i++)
			cout << a[i] << " ";
		cout << endl;
		return ;
	}
	for(int i = last +1 ; i <= n ; i++)
	{
		a[step] = i;
		f(i , step + 1);
	}
}
int main()
{
	cin >> n >> m;
	f(0 , 0);
	return 0;
}

#include<bits/stdc++.h>
using namespace std;
int boxes[25],n,m,numbers[105];
void dfs(int s){
	if(s > m){
		for(int i = 1;i <= m;i++){
			cout << boxes[i] << " ";
		}
		cout << endl;
		return;
	}
	for(int i = boxes[s - 1];i <= n;i++){
		if(not numbers[i]){
			numbers[i] = 1;
			boxes[s] = i;
			dfs(s + 1);
			numbers[i] = 0;
		}
	}
}
int main(){
	cin >> n >> m;
	boxes[0] = 1;
	dfs(1);

}

#include <bits/stdc++.h>
using namespace std;
const int N=1e2+10;
const int INF=0x3f3f3f3f;
int n,m,a[N];
void dfs(int x)
{
	if(x==n)
	{
		for(int i=1;i<=x;i++)
		{
			cout<<a[i];
		}
		cout<<endl;
		return;
	} 
	for(int i=a[x]+1;i<=m;i++)
	{
		a[x+1]=i;
		dfs(x+1);
		a[x+1]=0;
	}
}
int main()
{
	cin>>m>>n;
	dfs(0);
	return 0;
}