一、AcWing 338. 计数问题
1. 问题描述

2. 问题解决
#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
const int N = 10;
int get(vector<int> num, int l, int r)
{
int res = 0;
for (int i = l; i >= r; i -- ) res = res * 10 + num[i];
return res;
}
int power10(int x)
{
int res = 1;
while (x -- ) res *= 10;
return res;
}
int count(int n, int x)
{
if (!n) return 0;
vector<int> num;
while (n)
{
num.push_back(n % 10);
n /= 10;
}
n = num.size();
int res = 0;
for (int i = n - 1 - !x; i >= 0; i -- )
{
if (i < n - 1)
{
res += get(num, n - 1, i + 1) * power10(i);
if (!x) res -= power10(i);
}
if (num[i] == x) res += get(num, i - 1, 0) + 1;
else if (num[i] > x) res += power10(i);
}
return res;
}
int main()
{
int a, b;
while (cin >> a >> b , a)
{
if (a > b) swap(a, b);
for (int i = 0; i <= 9; i ++ )
cout << count(b, i) - count(a - 1, i) << ' ';
cout << endl;
}
return 0;
}
二、AcWing 291. 蒙德里安的梦想
1. 问题描述

2. 问题解决
#include <cstring>
#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
typedef long long LL;
const int N = 12, M = 1 << N;
int n, m;
LL f[N][M];
vector<int> state[M];
bool st[M];
int main()
{
while (cin >> n >> m, n || m)
{
for (int i = 0; i < 1 << n; i ++ )
{
int cnt = 0;
bool is_valid = true;
for (int j = 0; j < n; j ++ )
if (i >> j & 1)
{
if (cnt & 1)
{
is_valid = false;
break;
}
cnt = 0;
}
else cnt ++ ;
if (cnt & 1) is_valid = false;
st[i] = is_valid;
}
for (int i = 0; i < 1 << n; i ++ )
{
state[i].clear();
for (int j = 0; j < 1 << n; j ++ )
if ((i & j) == 0 && st[i | j])
state[i].push_back(j);
}
memset(f, 0, sizeof f);
f[0][0] = 1;
for (int i = 1; i <= m; i ++ )
for (int j = 0; j < 1 << n; j ++ )
for (auto k : state[j])
f[i][j] += f[i - 1][k];
cout << f[m][0] << endl;
}
return 0;
}
三、蓝桥杯十一届 植树
1. 问题描述

2. 问题解决
#include<bits/stdc++.h>
using namespace std;
const int N=35;
struct tree
{
int x,y,r,s;
};
bool cross[N][N];
tree t[N];
int maxa,n;
vector<int> plant;
bool judge(tree t1,tree t2)
{
if(pow(t1.x-t2.x,2)+pow(t1.y-t2.y,2)>= pow(t1.r+t2.r,2))
return false;
return true;
}
void dfs(int i,int ans)
{
if(i==n)
{
if(ans>maxa) maxa=ans;
return;
}
for(auto j:plant)
{
if(judge(t[i],t[j]))
{
dfs(i+1,ans);
return;
}
}
plant.push_back(i);
dfs(i+1,ans+t[i].s);
plant.pop_back();
dfs(i+1,ans);
return;
}
int main()
{
cin>>n;
for(int i=0;i<n;i++)
{
cin>>t[i].x>>t[i].y>>t[i].r;
t[i].s=t[i].r*t[i].r;
}
for(int i=1;i<n;i++)
{
cross[i][i]=true;
for(int j=0;j<i;j++)
{
cross[i][j]= judge(t[i],t[j]);
cross[j][i]=cross[i][j];
}
}
dfs(0,0);
cout<<maxa;
return 0;
}