向着CSP前进

#include <bits/stdc++.h>
using namespace std;
const int N = 10;
int n,book[N],a[N],L[N],R[N],res=1e9+10;
int judge(){
	int res = 0,now=1;
	for(int i=2;i<=n;i++){
		now=now+max(R[a[i-1]],L[a[i]])+1;
	}
	return now;
}
void dfs(int x){
	if(x>n){
		res = min(res,judge());
		return;
	}
	for(int i=1;i<=n;i++){
		if(book[i]==0){
			a[x] = i;
			book[i] = 1;
			dfs(x+1);
			book[i] = 0;
		}
	}
}
int main(){
	cin>>n;
	for(int i=1;i<=n;i++){
		cin>>L[i];
	}
	for(int i=1;i<=n;i++){
		cin>>R[i];
	}
	dfs(1);
	cout<<res<<endl;
	return 0;
}

#include <bits/stdc++.h>
using namespace std;
const int N = 55;
int n,k,a[N],book[N],num[N],res;
int isprime(int x){
	if(x<=1)return 0;
	int lim = sqrt(x);
	for(int i=2;i<=lim;i++){
		if(x%i==0)return 0;
	}
	return 1;
}
void dfs(int x,int id){
	if(x>k){
		int sum = 0;
		for(int i=1;i<=k;i++)sum+=a[i];
		if(isprime(sum))res++;
		return;
	}
	for(int i=id+1;i<=n;i++){
		if(book[i]==0){
			a[x] = num[i];
			book[i] = 1;
			dfs(x+1,i);
			book[i] = 0;
		}
	}
}
int jc(int x){
	int res = 1;
	for(int i=1;i<=x;i++)res*=i;
	return res;
}
int main(){
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	cin>>n>>k;
	for(int i=1;i<=n;i++){
		cin>>num[i];
	}
	dfs(1,0);
	cout<<res<<endl;
	return 0;
}

/*vector<char>mp[10005];
for(int i=0;i<n;++i){
	for(int j=0;j<m;++j){
		char m;
		cin>>m;
		mp[i].push_back(m);
	}
}
//访问 (x,y)  mp[x][y]

string mp[10005]; //mp[i]表示第i行*/

#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 5;
int n, m, ans;
int d[4][2] = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
string mp[N], vis[N]; //VIS是否已经访问过

void dfs(int x, int y ) {
	vis[x][y] = '1';
	if (mp[x][y] == 'S')
		ans++;
	else if (mp[x][y] == 'M')
		ans += 5;
	else
		ans += 10;
	for (int i = 0; i < 4; ++i) {
		int nx = x + d[i][0];
		int ny = y + d[i][1];
		if (nx >= 0 && nx < n && ny >= 0 && ny < m && mp[nx][ny] != '*' && vis[nx][ny] == '0')
			dfs(nx, ny);
	}
}

int main() {
	cin >> n >> m;
	for (int i = 0; i < n; ++i)
		cin >> mp[i]; //读地图
	for (int i = 0; i < n; ++i) {
		for (int j = 0; j < m; ++j) {
			vis[i] += '0';
		}
	}
	int start, end;
	cin >> start >> end;
	dfs(start, end);
	cout << ans;
	return 0;
}

// 装箱问题 给定n个物品，第i个物品的重量为ci,箱子的容量为w，求最少得箱子数量
/*
1个物品 有2种选择：
1.放到已经装有其他物品的箱子
2.重新放一个新箱子 k+1

剪枝优化：
1、如果某个方案用的箱子k>=ans。
2.优化搜索顺序剪枝 从大到小来进行DFS
*/
#include <bits/stdc++.h>
using namespace std;
int c[25], box[25], n, w, ans;

void dfs(int s, int k) { //处理第s个物品，当前已经用了k个箱子
	if (k >= ans)
		return; //剪枝1
	if (s > n) {
		ans = min(ans, k);
		return;
	}
	//尝试将第s个物品放入已经有前k个箱子里
	for (int i = 1; i <= k; ++i) {
		if (box[i] + c[s] <= w) {
			box[i] += c[s];
			dfs(s + 1, k);
			box[i] -= c[s];
		}
	}
	//尝试新开1个箱子
	box[k + 1] = c[s];
	dfs(s + 1, k + 1);
	box[k + 1] = 0;
}

int main() {
	cin >> n >> w;
	for (int i = 1; i <= n; ++i)
		cin >> c[i];
	sort(c + 1, c + n + 1, greater<int>()); //从大到小进行排序
	ans = n; //初始化最坏的情况，一个物品一个箱子
	dfs(1, 0); //从第1个物品开始，初始0个箱子
	cout << ans << endl;

	return 0;
}

#include <bits/stdc++.h>
using namespace std;
int n;
int l, r;
int w[50];
int z = 0;

void dfs(int x, int sum) {
	if (sum > r) {
		return;
	}
	if (x > n) {

		if (sum <= r && sum >= l ) {
			z++;
			
		}return;
	}
	dfs(x + 1, sum);
	dfs(x + 1, sum + w[x]);

}

int main() {
	cin >> n >> l >> r;
	for (int i = 1; i <= n; ++i) {
		cin >> w[i];
	}
	dfs(1, 0);
	cout << z;
	return 0;
}

  #include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 10, M = 1e2 + 10;
char a[M][M];

int d[4][2] = {{-1, 0}, {0, 1}, {1, 0}, {0, -1}};
int n, m;
bool b = 0;

void dfs(int x, int y) {
	if (x == n && y == m) {
		b = 1;
		return ;
	}
	if (a[x][y] == '#') {
		return;
	}
	int nx, ny;
	for (int i = 0; i < 4; i++) {
        a[x][y]='#';
		nx = x + d[i][0];
		ny = y + d[i][1];
        if(nx>=1&&nx<=n&&ny>=1&&ny<=m){
		dfs(nx, ny);
        }else{
            continue;
        }
	}
}

int main() {
	cin >> n >> m;
	for (int i = 1; i <= n; i++) {
		for (int j = 1; j <= m; j++) {
			cin >> a[i][j];
		}
	}
	dfs(1, 1);
	if (b == 1) {
		cout << "Yes";
	} else {
		cout << "No";
	}

	return 0;
}