题目链接：点击打开链接
题意：
给定n个数，随意排列。
给定k个违禁数b[]。
问：有多少个排列使得这个排列的 n项前缀和中不出现违禁数。
（formally，if it’s a legal permutation, sum[i] != b[j] (1<=i<=n, 1<=j<=k))
sum[0] = 0; sum[i] = sum[i-1]+a[permutaion[i]];
==java党表示被tle，心疼自己T^T
#include <stdio.h>const int N = 24;int dp[1<<N], a[N], b[N];int n, k;const int mod = 1e9+7;int main(){scanf("%d", &n);for(int i = 0; i < n; i++)scanf("%d", &a[i]);scanf("%d", &k);for(int i = 0; i < k; i++)scanf("%d", &b[i]);dp[0] = 1;for(int i = 1, sum; i < (1<<n); i++){sum = 0;for(int j = 0; j < n; j++)if(i&(1<<j)){dp[i] += dp[i^(1<<j)];if(dp[i]>=mod)dp[i] -= mod;sum += a[j];}for(int j = 0; j < k; j++)if(sum == b[j])dp[i] = 0;}printf("%d\n",dp[(1<<n)-1]);return 0;}任性附上java tle代码import java.io.BufferedReader;import java.io.InputStreamReader;import java.io.PrintWriter;import java.math.BigInteger;import java.text.DecimalFormat;import java.util.ArrayDeque;import java.util.ArrayList;import java.util.Arrays;import java.util.Collection;import java.util.Collections;import java.util.Comparator;import java.util.Deque;import java.util.HashMap;import java.util.Iterator;import java.util.LinkedList;import java.util.Map;import java.util.PriorityQueue;import java.util.Scanner;import java.util.Stack;import java.util.StringTokenizer;import java.util.TreeMap;import java.util.TreeSet;import java.util.Queue;import java.io.File;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.FileOutputStream;public class Main {int[] dp = new int[1<<N], a = new int[N], b = new int[N];int n, k;void work() throws Exception {n = Int();for(int i = 0; i < n; i++)a[i] = Int();k = Int();for(int i = 0; i < k; i++)b[i] = Int();dp[0] = 1;int all = 1<<n;for(int i = 1, sum; i < all; i++){sum = 0;for(int j = 0; j < n; j++)if((i&(1<<j))>0){dp[i] += dp[i^(1<<j)];if(dp[i]>=mod)dp[i] -= mod;sum += a[j];}for(int j = 0; j < k; j++)if(sum == b[j])dp[i] = 0;}out.println(dp[(1<<n)-1]);}public static void main(String[] args) throws Exception {Main wo = new Main();in = new BufferedReader(new InputStreamReader(System.in));out = new PrintWriter(System.out);// in = new BufferedReader(new InputStreamReader(new FileInputStream(new// File("input.txt"))));// out = new PrintWriter(new File("output.txt"));wo.work();out.close();}static int N = 24;static int M = N * 2;DecimalFormat df = new DecimalFormat("0.0000");static int inf = (int) 1e9;static long inf64 = (long) 1e18;static double eps = 1e-8;static double Pi = Math.PI;static int mod = (int) 1e9 + 7;private String Next() throws Exception {while (str == null || !str.hasMoreElements())str = new StringTokenizer(in.readLine());return str.nextToken();}private int Int() throws Exception {return Integer.parseInt(Next());}private long Long() throws Exception {return Long.parseLong(Next());}private double Double() throws Exception {return Double.parseDouble(Next());}StringTokenizer str;static Scanner cin = new Scanner(System.in);static BufferedReader in;static PrintWriter out;/* * class Edge{ int from, to, dis, nex; Edge(){} Edge(int from, int to, int * dis, int nex){ this.from = from; this.to = to; this.dis = dis; this.nex = * nex; } } Edge[] edge = new Edge[M<<1]; int[] head = new int[N]; int * edgenum; void init_edge(){ for(int i = 0; i < N; i++)head[i] = -1; * edgenum = 0;} void add(int u, int v, int dis){ edge[edgenum] = new * Edge(u, v, dis, head[u]); head[u] = edgenum++; }/* */int upper_bound(int[] A, int l, int r, int val) {// upper_bound(A+l,A+r,val)-A;int pos = r;r–;while (l <= r) {int mid = (l + r) >> 1;if (A[mid] <= val) {l = mid + 1;} else {pos = mid;r = mid – 1;}}return pos;}int lower_bound(int[] A, int l, int r, int val) {// upper_bound(A+l,A+r,val)-A;int pos = r;r–;while (l <= r) {int mid = (l + r) >> 1;if (A[mid] < val) {l = mid + 1;} else {pos = mid;r = mid – 1;}}return pos;}int Pow(int x, int y) {int ans = 1;while (y > 0) {if ((y & 1) > 0)ans *= x;y >>= 1;x = x * x;}return ans;}double Pow(double x, int y) {double ans = 1;while (y > 0) {if ((y & 1) > 0)ans *= x;y >>= 1;x = x * x;}return ans;}int Pow_Mod(int x, int y, int mod) {int ans = 1;while (y > 0) {if ((y & 1) > 0)ans *= x;ans %= mod;y >>= 1;x = x * x;x %= mod;}return ans;}long Pow(long x, long y) {long ans = 1;while (y > 0) {if ((y & 1) > 0)ans *= x;y >>= 1;x = x * x;}return ans;}long Pow_Mod(long x, long y, long mod) {long ans = 1;while (y > 0) {if ((y & 1) > 0)ans *= x;ans %= mod;y >>= 1;x = x * x;x %= mod;}return ans;}int gcd(int x, int y) {if (x > y) {int tmp = x;x = y;y = tmp;}while (x > 0) {y %= x;int tmp = x;x = y;y = tmp;}return y;}int max(int x, int y) {return x > y ? x : y;}int min(int x, int y) {return x < y ? x : y;}double max(double x, double y) {return x > y ? x : y;}double min(double x, double y) {return x < y ? x : y;}long max(long x, long y) {return x > y ? x : y;}long min(long x, long y) {return x < y ? x : y;}int abs(int x) {return x > 0 ? x : -x;}double abs(double x) {return x > 0 ? x : -x;}long abs(long x) {return x > 0 ? x : -x;}boolean zero(double x) {return abs(x) < eps;}double sin(double x) {return Math.sin(x);}double cos(double x) {return Math.cos(x);}double tan(double x) {return Math.tan(x);}double sqrt(double x) {return Math.sqrt(x);}}
，有的旅行时为了寻找逝去的年华，重温青春的惆怅。
