##1.计算系数
[移步洛谷](https://www.luogu.org/problemnew/solution/P1313)
##2.聪明的质检员
C++ 代码：
```
#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;
typedef long long LL; const int N = 200010;
int n, m;
LL S;
int w[N], v[N];
int l[N], r[N];
int cnt[N];
LL sum[N];
LL get(int W)
{
for (int i = 1; i <= n; i++)
if (w[i] >= W)
{
sum[i] = sum[i - 1] + v[i];
cnt[i] = cnt[i - 1] + 1;
}
else
{
sum[i] = sum[i - 1];
cnt[i] = cnt[i - 1];
}
LL res = 0;
for (int i = 0; i < m; i++) res += (cnt[r[i]] - cnt[l[i] - 1]) *(sum[r[i]] - sum[l[i] - 1]);
return res;
}
int main()
{
scanf("%d%d%lld", &n, &m, &S);
for (int i = 1; i <= n; i++) scanf("%d%d", &w[i], &v[i]);
for (int i = 0; i < m; i++) scanf("%d%d", &l[i], &r[i]);
int l = 0, r = 1e6 + 1;
while (l < r)
{
int mid = l + r + 1 >> 1;
if (get(mid) >= S) l = mid;
else r = mid - 1;
}
printf("%lld\n", min(abs(get(r) - S), abs(S - get(r + 1))));
return 0;
}
```
##3.观光公交
```
#include <iostream>
#include <algorithm>
using namespace std; const int N = 1010,
M = 10010;
int n, m, k;
int d[N];
int t[M], a[M], b[M];
int tm[N], last[N];
int sum[N];
int reduce[N];
int main()
{
scanf("%d%d%d", &n, &m, &k);
for (int i = 1; i < n; i++) scanf("%d", &d[i]);
for (int i = 0; i < m; i++)
{
scanf("%d%d%d", &t[i], &a[i], &b[i]);
last[a[i]] = max(last[a[i]], t[i]);
sum[b[i]]++;
}
for (int i = 1; i <= n; i++) tm[i] = max(tm[i - 1], last[i - 1]) + d[i - 1];
while (k--)
{
for (int i = n; i >= 2; i--)
if (!d[i - 1]) reduce[i - 1] = 0;
else
{
reduce[i - 1] = sum[i];
if (tm[i] > last[i]) reduce[i - 1] += reduce[i];
}
int p = 0;
for (int i = 1; i < n; i++)
if (reduce[p] < reduce[i])
p = i;
if (!p) break;
d[p]--;
for (int i = p + 1; i <= n; i++) tm[i] = max(tm[i - 1], last[i - 1]) + d[i - 1];
}
int res = 0;
for (int i = 0; i < m; i++) res += tm[b[i]] - t[i];
printf("%d\n", res);
return 0;
}
```