https://codeforces.com/contest/1400/problem/A
Example
input
4
1
1
3
00000
4
1110000
2
101
output
1
000
1010
00
思路：先贴下代码，有事要去医院，等会补上思路。
AC代码：
#include<bits/stdc++.h>
#define ms(a,b) memset(a,b,sizeof a)
using namespace std;
typedef long long ll;
void solve() {
int n; string s;
cin >> n >> s;
for (int i = 0; i < n; ++i)
cout << s[n - 1];
cout << endl;
}
int main() {
//freopen("in.txt", "r", stdin);
ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
int t; cin >> t;
while (t--)solve();
}
https://codeforces.com/contest/1400/problem/B
Example
input
3
33 27
6 10
5 6
100 200
10 10
5 5
1 19
1 3
19 5
output
11
20
3
思路：
AC代码：
#include<bits/stdc++.h>
#define ms(a,b) memset(a,b,sizeof a)
using namespace std;
const int N = 1e5 + 100;
typedef long long ll;
ll n, m, a[N];
void solve() {
int p, f;
cin >> p >> f;
int cnts, cntw, s, w;
cin >> cnts >> cntw >> s >> w;
if (s > w) {
swap(s, w);
swap(cnts, cntw);
}
int maxi = 0;
for (int i = 0; i <= min(cnts, p / s); i++) {
int a = min(cntw, (p - i * s) / w);
int b = min(cnts - i, f / s);
int c = min(cntw - a, (f - b * s) / w);
maxi = max(maxi, a + b + c + i);
}
cout << maxi << '
';
}
int main() {
//freopen("in.txt", "r", stdin);
ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
int t; cin >> t;
while (t--)solve();
}
https://codeforces.com/contest/1400/problem/C
Example
input
3
101110
2
01
1
110
1
output
111011
10
-1
思路：
AC代码：
#include<bits/stdc++.h>
#define ms(a,b) memset(a,b,sizeof a)
using namespace std;
const int N = 1e5 + 100;
typedef long long ll;
ll n, m, a[N];
void solve() {
ll x; string s, ss = "";
cin >> s >> x;
int n = s.size();
for (int i = 0; i < n; ++i) ss += '1';
for (int i = 0; i < n; ++i) {
if (s[i] == '0' && i + x < n)ss[i + x] = '0';
if (s[i] == '0' && i - x >= 0)ss[i - x] = '0';
}
bool flag = true;
for (int i = 0; i < n; ++i) {
if (s[i] == '1') {
bool ok = false;
if (i + x < n && ss[i + x] == '1') ok = true;
if (i - x >= 0 && ss[i - x] == '1') ok = true;
if (!ok) flag = false;
}
}
if (!flag)cout << -1 << endl;
else cout << ss << endl;
}
int main() {
//freopen("in.txt", "r", stdin);
ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
int t; cin >> t;
while (t--)solve();
}
https://codeforces.com/contest/1400/problem/D
Example
input
2
5
2 2 2 2 2
6
1 3 3 1 2 3
output
5
2
思路：
AC代码： 使用map，900+ms
#include<bits/stdc++.h>
#define ms(a,b) memset(a,b,sizeof a)
using namespace std;
const int N = 1e5 + 100;
typedef long long ll;
ll a[N];
map<int, int>m1, m2;
void solve() {
m1.clear();
int n; cin >> n;
for (int i = 0; i < n; ++i)cin >> a[i];
ll ans = 0;
for (int i = 0; i < n; ++i) {
m2.clear();
for (int j = n - 1; j > i; --j)
ans += m1[a[j]] * m2[a[i]], ++m2[a[j]];
++m1[a[i]];
}
cout << ans << endl;
}
int main() {
//freopen("in.txt", "r", stdin);
ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
int t; cin >> t;
while (t--)solve();
}