POJ 3187 Backward Digit Sums 枚举

用next_permutation枚举全排列。

//#pragma comment(linker, "/STACK:1024000000,1024000000")
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#include<iostream>
#include<sstream>
#include<cmath>
#include<climits>
#include<string>
#include<map>
#include<queue>
#include<vector>
#include<stack>
#include<set>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;
#define pb(a) push(a)
#define INF 0x1f1f1f1f
#define lson idx<<1,l,mid
#define rson idx<<1|1,mid+1,r
#define PI  3.1415926535898
template<class T> T min(const T& a,const T& b,const T& c) {
    return min(min(a,b),min(a,c));
}
template<class T> T max(const T& a,const T& b,const T& c) {
    return max(max(a,b),max(a,c));
}
void debug() {
#ifdef ONLINE_JUDGE
#else

    freopen("in.txt","r",stdin);
    //freopen("d:\out1.txt","w",stdout);
#endif
}
int getch() {
    int ch;
    while((ch=getchar())!=EOF) {
        if(ch!=' '&&ch!='
')return ch;
    }
    return EOF;
}

const int maxn=12;
int ans[maxn];
int n;
int check()
{
    int res[maxn][maxn];
    for(int i=0;i<n;i++)
        res[n][i]=ans[i];
    for(int i=n-1;i>=1;i--)
    {
        for(int j=0;j<i;j++)
            res[i][j]=res[i+1][j]+res[i+1][j+1];
    }
    return res[1][0];
}
int main()
{
    int K;
    while(scanf("%d%d",&n,&K)!=EOF)
    {
        for(int i=1;i<=n;i++)
            ans[i-1]=i;
        do
        {
            if(check()==K)break;
        }while(next_permutation(ans,ans+n));
        for(int i=0;i<n;i++)
            printf("%d%c",ans[i],i==n-1?'
':' ');
    }
    return 0;
}