C++ :

#include <cstdio>
/* 最终结果 = Σ C(n-1,i) * p[i]。从左到右按值升序 DFS，
   用「剩余系数 × 剩余可用值」的上下界剪枝，首个解即字典序最小。 */
static int n, used[13], perm[13], found;
static long long target, coef[13];
void dfs(int p, long long cur){
    if(found) return;
    if(p == n){ if(cur == target) found = 1; return; }
    int avail[13], ac = 0;
    for(int v = 1; v <= n; v++) if(!used[v]) avail[ac++] = v;   /* 升序 */
    long long cs[13];
    int k = n - p;
    for(int i = 0; i < k; i++) cs[i] = coef[p + i];
    for(int i = 0; i < k; i++)
        for(int j = i + 1; j < k; j++)
            if(cs[i] > cs[j]){ long long t = cs[i]; cs[i] = cs[j]; cs[j] = t; }
    long long mn = 0, mx = 0;
    /* 重排不等式：大系数配小值最小，大系数配大值最大 */
    for(int i = 0; i < k; i++) mn += cs[k - 1 - i] * avail[i];
    for(int i = 0; i < k; i++) mx += cs[i] * avail[i];
    if(cur + mn > target || cur + mx < target) return;
    for(int i = 0; i < ac; i++){
        int v = avail[i];
        used[v] = 1; perm[p] = v;
        dfs(p + 1, cur + coef[p] * v);
        used[v] = 0;
        if(found) return;
    }
}
int main(){
    long long sum;
    if(scanf("%d %lld", &n, &sum) != 2) return 0;
    target = sum;
    coef[0] = 1;
    for(int i = 1; i < n; i++) coef[i] = coef[i - 1] * (n - i) / i;
    for(int i = 1; i <= n; i++) used[i] = 0;
    found = 0;
    dfs(0, 0);
    if(found){
        for(int i = 0; i < n; i++) printf("%d%c", perm[i], i + 1 == n ? '\n' : ' ');
    }
    return 0;
}