8.27_407_课堂总结 - 洛谷保存站

# U593635 交换
$\color{#52c41a} 100pts$
### 思路
模拟
## 代码
```cpp
#include<bits/stdc++.h>
#define ll long long
using namespace std;
int main(){
	ios::sync_with_stdio(false);
	cin.tie(0);cout.tie(0);
	int a[4];
	cin >> a[1] >> a[2] >> a[3];
	swap(a[1], a[2]);
	swap(a[1], a[3]);
	for(int i = 1; i <= 3; i++){
		cout << a[i] << ' ';
	}
	return 0;
}
```
# 	T643661 猜猜芭蕾舞剧将如何结束
$\color{#52c41a} 100pts$
### 思路
模拟
## 代码
```cpp
#include<bits/stdc++.h>
#define ll long long
using namespace std;
int main(){
	ios::sync_with_stdio(false);
	cin.tie(0);cout.tie(0);
	ll m, n, lp = 0, rp;
	cin >> m >> n;
	rp = m;
	for(int i = 1; i <= n; i++){
		ll x;
		cin >> x;
		if(x < 0){
			lp = max((ll)0, lp + x);
			rp = max((ll)0, rp + x);
		}else{
			lp = min(m, lp + x);
			rp = min(m, rp + x);
		}
	}
	if(lp == rp){
		cout << lp;
	}else{
		cout << -1;
	}
	return 0;
}
```
# U593646 落落的去的数学问题五
$\color{#ffc116} 65pts$

暴力
### 思路
BFS
## 代码
```cpp
#include<bits/stdc++.h>
#define ll long long
#define ull unsigned ll
using namespace std;
int k;
string ans[200001];

void bfs(){
	queue<string> q;
	for(int i = 1; i <= 9; i++){
		q.push(to_string(i));
	}
	int cnt = 9;
	while(q.size()){
		string f = q.front();
		q.pop();
		if(cnt > k){
			return;
		}
		if(f[f.size() - 1] > '0'){
			ans[++cnt] = f + (char)(f[f.size() - 1] - 1);
			q.push(f + (char)(f[f.size() - 1] - 1));
		}
		ans[++cnt] = f + f[f.size() - 1];
		q.push(f + f[f.size() - 1]);
		if(f[f.size() - 1] < '9'){
			ans[++cnt] = f + (char)(f[f.size() - 1] + 1);
			q.push(f + (char)(f[f.size() - 1] + 1));
		}
	}
}

int main(){
	ios::sync_with_stdio(false);
	cin.tie(0);cout.tie(0);
	cin >> k;
	if(k < 10){
		cout << k;
		return 0;
	}
	bfs();
	cout << ans[k];
	return 0;
}
```
# U593645 操作2
$\color{#e74c3c} 0pts$

时间不够了QAQ
### 思路
前缀和 + 二分（不开long long见祖宗）
## 代码
```cpp
#include<bits/stdc++.h>
#define int long long
#define ll long long
using namespace std;
int n, m;
int a[200001];
ll cnt[200001];
signed main(){
	ios::sync_with_stdio(false);
	cin.tie(0);cout.tie(0);
	cin >> n >> m;
	for(int i = 1; i <= n; i++){
		cin >> a[i];
	}
	stable_sort(a + 1, a + n + 1);
	for(int i = 1; i <= n; i++){
		cnt[i] = cnt[i - 1] + a[i];
	}
	for(int i = 1; i <= m; i++){
		int x;
		cin >> x;
		ll ans = 0;
		int l = lower_bound(a + 1, a + n + 1, x) - a - 1;
		int sum = cnt[l] - cnt[0];
		int tmp = x * l;
		ans += abs(tmp - sum);
		l = upper_bound(a + 1, a + n + 1, x) - a;
		sum = cnt[n] - cnt[l - 1];
		tmp = x * (n - l + 1);
		ans += abs(tmp - sum);
		cout << ans << "\n";
	}
	return 0;
}
```

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