第五题
抽卡游戏，n张普通卡，m张ssr，抽到ssr花费2金币不放回，抽到普通卡1金币放回，求取完所有ssr的期望金币数
1 #include <iostream> 2 using namespace std; 3 double ans; 4 int main() 5 { 6 int n, m; cin >> n >> m; 7 for(int i=1; i<=m; i++) 8 ans += 2.0 + double(n) / double(i); 9 printf("%.2lf ", ans); 10 return 0; 11 }
第四题
1 #include<bits/stdc++.h> 2 using namespace std; 3 typedef long long LL; 4 const int N = 1e5 + 7; 5 LL dp[N][4]; 6 int n; 7 int main() 8 { 9 cin >> n; 10 string str; 11 cin >> str; 12 for(int i=1; i<=n; i++) { 13 for(int j=0; j<4; j++) dp[i][j] = dp[i-1][j]; 14 15 if(str[i-1] == 'S') dp[i][0] += 1; 16 else if(str[i-1] == 'T') { 17 if(i>=2) dp[i][1] += dp[i-2][0]; 18 } 19 else if(str[i-1] == 'A') { 20 if(i>=2) dp[i][2] += dp[i-2][1]; 21 } 22 else if(str[i-1] == 'R') { 23 if(i>=2) dp[i][3] += dp[i-2][2]; 24 } 25 26 } 27 cout << dp[n][3] << endl; 28 return 0; 29 }
第三题 dfs爆栈 bfs
#include <bits/stdc++.h>
using namespace std;
const int N = 1e3 + 7;
struct node {
int x, y;
};
int dx[] = {1, 2, 2, 1, -1, -2, -2, -1};
int dy[] = {-2, -1, 1, 2, 2, 1, -1, -2};
int n, m;
string mp[N];
bool vis[N][N];
queue<node>
int ans;
bool isok(int x, int y) {
return x>=0 && x<n && y>=0 && y<m;
}
void bfs(int x, int y) {
node start = {x, y};
q.push(start); vis[x][y] = 1;
ans += 1;
while(!q.empty()) {
node now = q.front(); q.pop();
x = now.x;
y = now.y;
for(int i=0; i<8; i++) {
int tx = x + dx[i];
int ty = y + dy[i];
if(isok(tx, ty) && mp[x][y] != mp[tx][ty] && !vis[tx][ty]) {
node tmp = {tx, ty};
q.push(tmp); vis[tx][ty] = 1;
ans += 1;
}
}
}
}
int main()
{
cin >> n >> m;
for(int i=0; i<n; i++)
cin >> mp[i];
int x, y;
cin >> x >> y;
dfs(x-1, y-1);
cout << ans << endl;
return 0;
}
第二题 二分
x^k = y
x + y = b
(k>0, b>0) 求两条曲线在第一象限的相交面积
1 #include <bits/stdc++.h> 2 using namespace std; 3 int k, b; 4 double binary_search(int k, int b) { 5 double l = 0, r = b; 6 while(l<=r) { 7 double mid = (l+r) * 0.5; 8 if(k * log(mid) > log(1e6)) { 9 r = mid; 10 continue; 11 } 12 if(abs(mid + pow(mid, k) - b) < 1e-9) return mid; 13 else if(mid + pow(mid, k) > b) r = mid; 14 else l = mid; 15 } 16 return l; 17 } 18 int main() 19 { 20 cin >> k >> b; 21 double x = binary_search(k, b); 22 // printf("%lf %lf ", x, x + pow(x, k)); 23 double area = pow(x, k+1) / (k+1) + pow(x, k) * pow(x, k) * 0.5; 24 printf("%.6lf ", area); 25 return 0; 26 }
第一题 二分
#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
struct node {
double val;
int x, y;
bool operator<(const node& a) const {
return val < a.val;
}
};
LL w[507];
vector<node> num;
int n, m;
int binary_search(LL x) {
double key = log(x);
int l = 0, r = num.size() - 1;
while(l<=r) {
int mid = (l+r) / 2;
if(abs(num[mid].val - key) <= 1e-9) return mid;
else if(num[mid].val > key) r = mid - 1;
else l = mid + 1;
}
return -1;
}
int main()
{
cin >> n >> m;
for(int i=0; i<n; i++) cin >> w[i];
for(int i=0; i<n; i++)
for(int j=i+1; j<n; j++) {
double val = log(w[i]) * w[j];
node tmp = {val, i, j};
num.push_back(tmp);
val = log(w[j]) * w[i];
node ttmp = {val, j, i};
num.push_back(ttmp);
}
sort(num.begin(), num.end());
for(int i=0; i<m; i++) {
LL x; cin >> x;
int pos = binary_search(x);
if(pos == -1) cout << "-1 -1
";
else cout << w[num[pos].x] << " " << w[num[pos].y] << endl;
}
return 0;
}