Codeforces Round #642 (Div. 3)
还是视频题解。这次录的心态有点炸，录完了发现没开麦克风。。又得再录一次。
题目不算很难，可能就F需要好好想一下，一开始写了个假的\(dp：dp[i][j][0/1]\)表示当前在\((i,j)\)位置，\(a_{i,j}\)是否发生了变化，维护一个\(pair\)，一个是当前最小花费，另一个是当前\(a_{i,j}\)的值。但是写完了发现样例都过不了。但貌似这是个假的dp，不满足最优子结构。。。
但其实F注意一下有个点权值不变，那么这样就很好dp了。
E的话也不难，就是个线性dp。
代码如下：
A. Most Unstable Array
/*
* Author: heyuhhh
* Created Time: 2020/5/15 9:18:11
*/
#include <iostream>
#include <algorithm>
#include <cstring>
#include <cstdio>
#include <vector>
#include <cmath>
#include <set>
#include <map>
#include <queue>
#include <iomanip>
#include <assert.h>
#define MP make_pair
#define fi first
#define se second
#define pb push_back
#define sz(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()
#define INF 0x3f3f3f3f
#define Local
#ifdef Local
#define dbg(args...) do { cout << #args << " -> "; err(args); } while (0)
void err() { std::cout << std::endl; }
template<typename T, typename...Args>
void err(T a, Args...args) { std::cout << a << ' '; err(args...); }
template <template<typename...> class T, typename t, typename... A>
void err(const T <t> &arg, const A&... args) {
for (auto &v : arg) std::cout << v << ' '; err(args...); }
#else
#define dbg(...)
#endif
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
//head
const int N = 1e5 + 5;
void run() {
int n, m; cin >> n >> m;
if (n == 1) cout << 0 << '\n';
else if (n == 2) cout << m << '\n';
else cout << 2 * m << '\n';
}
int main() {
ios::sync_with_stdio(false);
cin.tie(0); cout.tie(0);
cout << fixed << setprecision(20);
int T; cin >> T; while(T--)
run();
return 0;
}
B. Two Arrays And Swaps
/*
* Author: heyuhhh
* Created Time: 2020/5/15 9:14:30
*/
#include <bits/stdc++.h>
#define MP make_pair
#define fi first
#define se second
#define pb push_back
#define sz(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()
#define INF 0x3f3f3f3f
#define Local
#ifdef Local
#define dbg(args...) do { cout << #args << " -> "; err(args); } while (0)
void err() { std::cout << std::endl; }
template<typename T, typename...Args>
void err(T a, Args...args) { std::cout << a << ' '; err(args...); }
template <template<typename...> class T, typename t, typename... A>
void err(const T <t> &arg, const A&... args) {
for (auto &v : arg) std::cout << v << ' '; err(args...); }
#else
#define dbg(...)
#endif
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
//head
const int N = 1e5 + 5;
void run() {
int n, k; cin >> n >> k;
vector <int> a(n), b(n);
for (int i = 0; i < n; i++) {
cin >> a[i];
}
for (int i = 0; i < n; i++) {
cin >> b[i];
}
sort(all(a));
sort(all(b)), reverse(all(b));
for (int i = 0; i < k; i++) {
if (a[i] < b[i]) swap(a[i], b[i]);
}
cout << accumulate(all(a), 0) << '\n';
}
int main() {
ios::sync_with_stdio(false);
cin.tie(0); cout.tie(0);
cout << fixed << setprecision(20);
int T; cin >> T; while(T--)
run();
return 0;
}
C. Board Moves
/*
* Author: heyuhhh
* Created Time: 2020/5/15 9:11:42
*/
#include <iostream>
#include <algorithm>
#include <cstring>
#include <cstdio>
#include <vector>
#include <cmath>
#include <set>
#include <map>
#include <queue>
#include <iomanip>
#include <assert.h>
#define MP make_pair
#define fi first
#define se second
#define pb push_back
#define sz(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()
#define INF 0x3f3f3f3f
#define Local
#ifdef Local
#define dbg(args...) do { cout << #args << " -> "; err(args); } while (0)
void err() { std::cout << std::endl; }
template<typename T, typename...Args>
void err(T a, Args...args) { std::cout << a << ' '; err(args...); }
template <template<typename...> class T, typename t, typename... A>
void err(const T <t> &arg, const A&... args) {
for (auto &v : arg) std::cout << v << ' '; err(args...); }
#else
#define dbg(...)
#endif
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
//head
const int N = 1e5 + 5;
void run() {
int n; cin >> n;
n >>= 1;
ll res = 1ll * n * (n + 1) * (2 * n + 1) / 6 * 8;
cout << res << '\n';
}
int main() {
ios::sync_with_stdio(false);
cin.tie(0); cout.tie(0);
cout << fixed << setprecision(20);
int T; cin >> T; while(T--)
run();
return 0;
}
D. Constructing the Array
/*
* Author: heyuhhh
* Created Time: 2020/5/15 0:08:23
*/
#include <iostream>
#include <algorithm>
#include <cstring>
#include <cstdio>
#include <vector>
#include <cmath>
#include <set>
#include <map>
#include <queue>
#include <iomanip>
#include <assert.h>
#define MP make_pair
#define fi first
#define se second
#define pb push_back
#define sz(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()
#define INF 0x3f3f3f3f
#define Local
#ifdef Local
#define dbg(args...) do { cout << #args << " -> "; err(args); } while (0)
void err() { std::cout << std::endl; }
template<typename T, typename...Args>
void err(T a, Args...args) { std::cout << a << ' '; err(args...); }
template <template<typename...> class T, typename t, typename... A>
void err(const T <t> &arg, const A&... args) {
for (auto &v : arg) std::cout << v << ' '; err(args...); }
#else
#define dbg(...)
#endif
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
//head
const int N = 2e5 + 5;
struct node {
int l, len;
bool operator < (const node &A) const {
if (len != A.len) return len < A.len;
return l > A.l;
}
};
void run() {
int n; cin >> n;
priority_queue <node> q;
q.push(node{1, n});
int T = 0;
vector <int> a(n + 1);
while (!q.empty()) {
++T;
node cur = q.top(); q.pop();
int l = cur.l, r = cur.l + cur.len - 1;
int m = (l + r) / 2;
a[m] = T;
if (cur.len & 1) {
if (m > l) q.push(node{l, cur.len / 2});
} else {
if (m > l) q.push(node{l, cur.len / 2 - 1});
}
if (m < r) q.push(node{l + (cur.len + 1) / 2, cur.len / 2});
}
for (int i = 1; i <= n; i++) {
cout << a[i] << " \n"[i == n];
}
}
int main() {
ios::sync_with_stdio(false);
cin.tie(0); cout.tie(0);
cout << fixed << setprecision(20);
int T; cin >> T; while(T--)
run();
return 0;
}
E. K-periodic Garland
/*
* Author: heyuhhh
* Created Time: 2020/5/14 23:57:45
*/
#include <iostream>
#include <algorithm>
#include <cstring>
#include <cstdio>
#include <vector>
#include <cmath>
#include <set>
#include <map>
#include <queue>
#include <iomanip>
#include <assert.h>
#define MP make_pair
#define fi first
#define se second
#define pb push_back
#define sz(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()
#define INF 0x3f3f3f3f
#define Local
#ifdef Local
#define dbg(args...) do { cout << #args << " -> "; err(args); } while (0)
void err() { std::cout << std::endl; }
template<typename T, typename...Args>
void err(T a, Args...args) { std::cout << a << ' '; err(args...); }
template <template<typename...> class T, typename t, typename... A>
void err(const T <t> &arg, const A&... args) {
for (auto &v : arg) std::cout << v << ' '; err(args...); }
#else
#define dbg(...)
#endif
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
//head
void run() {
int n, k; cin >> n >> k;
vector <int> dp(n + 1), sum(n + 1);
string s; cin >> s;
for (int i = 0; i < n; i++) {
sum[i + 1] = sum[i] + (s[i] == '1');
}
if (sum[n] == 0) {
cout << 0 << '\n';
return;
}
int ans = INF;
for (int i = 0; i < n; i++) {
int res = sum[i] + sum[n] - sum[i + 1];
res += (s[i] == '0');
ans = min(ans, res);
}
auto calc = [&] (int l, int r) {
return sum[r] - sum[l - 1];
};
dp[0] = 0;
for (int i = 1; i <= n; i++) {
dp[i] = sum[i - 1] + (s[i - 1] == '0');
if (i >= k) {
dp[i] = min(dp[i], dp[i - k] + calc(i - k + 1, i - 1) + (s[i - 1] == '0'));
}
}
for (int i = 1; i <= n; i++) {
ans = min(ans, dp[i] + sum[n] - sum[i]);
}
cout << ans << '\n';
}
int main() {
ios::sync_with_stdio(false);
cin.tie(0); cout.tie(0);
cout << fixed << setprecision(20);
int T; cin >> T; while(T--)
run();
return 0;
}
F. Decreasing Heights
/*
* Author: heyuhhh
* Created Time: 2020/5/14 22:53:49
*/
#include <iostream>
#include <algorithm>
#include <cstring>
#include <cstdio>
#include <vector>
#include <cmath>
#include <set>
#include <map>
#include <queue>
#include <iomanip>
#include <assert.h>
#define MP make_pair
#define fi first
#define se second
#define pb push_back
#define sz(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()
#define INF 0x3f3f3f3f3f3f3f3f
//#define Local
#ifdef Local
#define dbg(args...) do { cout << #args << " -> "; err(args); } while (0)
void err() { std::cout << std::endl; }
template<typename T, typename...Args>
void err(T a, Args...args) { std::cout << a << ' '; err(args...); }
template <template<typename...> class T, typename t, typename... A>
void err(const T <t> &arg, const A&... args) {
for (auto &v : arg) std::cout << v << ' '; err(args...); }
#else
#define dbg(...)
#endif
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
//head
const int N = 100 + 5;
int n, m;
ll a[N][N], dp[N][N];
void run() {
cin >> n >> m;
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= m; j++) {
cin >> a[i][j];
}
}
auto calc = [&](int sx, int sy, int ex, int ey, int op) {
int x, y;
if (op == 0) x = ex, y = ey;
else x = sx, y = sy;
ll res = 0;
for (int i = sx; i <= ex; i++) {
for (int j = sy; j <= ey; j++) {
int d = abs(x - i) + abs(y - j);
if (op == 0) {
if (a[i][j] >= a[x][y] - d) {
dp[i][j] = min(dp[i - 1][j], dp[i][j - 1]) + a[i][j] - a[x][y] + d;
}
} else {
if (a[i][j] >= a[x][y] + d) {
dp[i][j] = min(dp[i - 1][j], dp[i][j - 1]) + a[i][j] - a[x][y] - d;
}
}
}
}
return 0;
};
ll res = INF;
for (int x = 1; x <= n; x++) {
for (int y = 1; y <= m; y++) {
for (int i = 0; i <= n; i++) {
for (int j = 0; j <= m; j++) {
dp[i][j] = INF;
}
}
dp[1][0] = 0;
calc(1, 1, x, y, 0);
calc(x, y, n, m, 1);
res = min(res, dp[n][m]);
}
}
cout << res << '\n';
}
int main() {
ios::sync_with_stdio(false);
cin.tie(0); cout.tie(0);
cout << fixed << setprecision(20);
int T; cin >> T; while(T--)
run();
return 0;
}
重要的是自信，一旦有了自信，人就会赢得一切。
