2025.2.9——1400
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二进制/贪心+博弈/结论+结论/贪心/栈+二分+字符串
A
- 入手：分别考虑每一位。
- 关键：贪心。
- 巧妙：交换。
B
- 关键：换一种方式考虑每一个选与不选对答案的影响，从而发现结论。
C
- 入手：\(n==2\) 时模拟发现。
- 关键：贪心匹配的方式，排序后对于每一个 \(r\) 匹配最近且未配对的 \(l\) 。
- 巧妙：用栈去优化配对方式。
D
- 入手：二分很明显。
- 关键：维护一个区间而不是一个点。
- 巧妙：一种代码适用于两种情况。
E
- 入手：模拟一下。每次操作使子串中的最后一个字母去掉。
- 关键：必要次数将单调不增的子串操作至单调不减。次数为原始长度-前缀相同的个数。
------------------------代码------------------------
A
#include <bits/stdc++.h>
#define int long long //
#define endl '\n' // attention: interactive/debug
#define el cout << endl
using namespace std;
#define bug(BUG) cout << "bug:# " << (BUG) << endl
#define bug2(BUG1, BUG2) cout << "bug:# " << (BUG1) << " " << (BUG2) << endl
#define bug3(BUG1, BUG2, BUG3) cout << "bug:# " << (BUG1) << ' ' << (BUG2) << ' ' << (BUG3) << endl
#define bugv(VEC, ST) \
{ \
for (int I = ST; I < VEC.size(); I++) \
cout << VEC[I] << ' '; \
el; \
}
void _();
signed main()
{
ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
cout << fixed << setprecision(10);
int T = 1;
cin >> T;
while (T--)
_();
return 0;
}
void _()
{
int a, b, r;
cin >> a >> b >> r;
if (a < b)
swap(a, b);
bool fir = 1;
int res = 0;
for (int i = 60; i >= 0; i--)
{
int bit_a = a >> i & 1;
int bit_b = b >> i & 1;
if (bit_a - bit_b)
{
if (fir)
{
fir = 0;
res += 1ll << i;
}
else
{
if (bit_b)
res -= 1ll << i;
else if (r - (1ll << i) >= 0)
res -= 1ll << i, r -= 1ll << i;
else
res += 1ll << i;
}
}
}
cout << res;
el;
}
B
#include <bits/stdc++.h>
#define int long long //
#define endl '\n' // attention: interactive/debug
#define el cout << endl
using namespace std;
#define bug(BUG) cout << "bug:# " << (BUG) << endl
#define bug2(BUG1, BUG2) cout << "bug:# " << (BUG1) << " " << (BUG2) << endl
#define bug3(BUG1, BUG2, BUG3) cout << "bug:# " << (BUG1) << ' ' << (BUG2) << ' ' << (BUG3) << endl
#define bugv(VEC, ST) \
{ \
for (int I = ST; I < VEC.size(); I++) \
cout << VEC[I] << ' '; \
el; \
}
void _();
signed main()
{
ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
cout << fixed << setprecision(10);
int T = 1;
cin >> T;
while (T--)
_();
return 0;
}
void _()
{
int n;
cin >> n;
struct Node
{
int a, b;
};
vector<Node> a(n);
for (auto &[a, b] : a)
cin >> a;
for (auto &[a, b] : a)
cin >> b;
sort(a.begin(), a.end(), [](Node &e1, Node &e2)
{ return e1.a + e1.b > e2.a + e2.b; });
int res = 0;
int f = 1;
for (auto [x, y] : a)
{
if (f)
res += x - 1;
else
res -= y - 1;
f ^= 1;
}
cout << res;
el;
}
C
#include <bits/stdc++.h>
#define int long long //
#define endl '\n' // attention: interactive/debug
#define el cout << endl
using namespace std;
#define bug(BUG) cout << "bug:# " << (BUG) << endl
#define bug2(BUG1, BUG2) cout << "bug:# " << (BUG1) << " " << (BUG2) << endl
#define bug3(BUG1, BUG2, BUG3) cout << "bug:# " << (BUG1) << ' ' << (BUG2) << ' ' << (BUG3) << endl
#define bugv(VEC, ST) \
{ \
for (int I = ST; I < VEC.size(); I++) \
cout << VEC[I] << ' '; \
el; \
}
void _();
signed main()
{
ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
cout << fixed << setprecision(10);
int T = 1;
cin >> T;
while (T--)
_();
return 0;
}
void _()
{
int n;
cin >> n;
vector<pair<int, int>> a(n << 1);
vector<int> w(n);
int cnt = n;
for (auto &[x, y] : a)
{
cin >> x;
y = cnt > 0 ? 1 : -1;
cnt--;
}
for (auto &x : w)
cin >> x;
sort(w.begin(), w.end());
sort(a.begin(), a.end());
vector<int> stk, len;
for (auto [x, y] : a)
{
if (y == 1)
stk.push_back(x);
else
{
len.push_back(x - stk.back());
stk.pop_back();
}
}
sort(len.rbegin(), len.rend());
int res = 0;
for (int i = 0; i < n; i++)
res += len[i] * w[i];
cout << res;
el;
}
D
#include <bits/stdc++.h>
#define int long long //
#define endl '\n' // attention: interactive/debug
#define el cout << endl
using namespace std;
#define bug(BUG) cout << "bug:# " << (BUG) << endl
#define bug2(BUG1, BUG2) cout << "bug:# " << (BUG1) << " " << (BUG2) << endl
#define bug3(BUG1, BUG2, BUG3) cout << "bug:# " << (BUG1) << ' ' << (BUG2) << ' ' << (BUG3) << endl
#define bugv(VEC, ST) \
{ \
for (int I = ST; I < VEC.size(); I++) \
cout << VEC[I] << ' '; \
el; \
}
void _();
signed main()
{
ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
cout << fixed << setprecision(10);
int T = 1;
cin >> T;
while (T--)
_();
return 0;
}
void _()
{
int n;
cin >> n;
vector<pair<int, int>> a(n + 1);
for (int i = 1; i <= n; i++)
cin >> a[i].first >> a[i].second;
auto ok = [&](int x)
{
int l = 0, r = 0;
for (int i = 1; i <= n; i++)
{
l = max(a[i].first, l - x); // 找到一种方式适用于两种情况
r = min(a[i].second, r + x);
if (l > r)
return 0;
}
return 1;
};
int l = -1, r = 1e12;
while (r - l - 1)
{
int mid = l + r >> 1;
if (ok(mid))
r = mid;
else
l = mid;
}
cout << r;
el;
}
E
#include <bits/stdc++.h>
#define int long long //
#define endl '\n' // attention: interactive/debug
#define el cout << endl
using namespace std;
#define bug(BUG) cout << "bug:# " << (BUG) << endl
#define bug2(BUG1, BUG2) cout << "bug:# " << (BUG1) << " " << (BUG2) << endl
#define bug3(BUG1, BUG2, BUG3) cout << "bug:# " << (BUG1) << ' ' << (BUG2) << ' ' << (BUG3) << endl
#define bugv(VEC) \
{ \
for (auto Vec : VEC) \
cout << Vec << ' '; \
el; \
}
void _();
signed main()
{
ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
cout << fixed << setprecision(10);
int T = 1;
cin >> T;
while (T--)
_();
return 0;
}
void _()
{
int n;
cin >> n;
string s;
cin >> s;
string t = s;
sort(t.begin(), t.end());
if (t == s)
{
cout << 0;
el;
return;
}
char op = s[n - 1];
vector<int> id{n - 1};
for (int i = n - 2; i >= 0; i--)
if (s[i] >= s[id.back()])
id.push_back(i);
int res = id.size() - 1;
for (int i = id.size() - 2; i >= 0; i--)
if (s[id[i]] == s[id[id.size() - 1]])
res--;
else
break;
for (int l = 0, r = id.size() - 1; l < r; l++, r--)
swap(s[id[l]], s[id[r]]);
// bugv(id);
// bug(s);
t = s;
sort(t.begin(), t.end());
if (t != s)
res = -1;
cout << res;
el;
}
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