A题：
#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
const int co[2][2] = { 1, 0, 0, 1 };
int ans = 0;
int n = 17, m = 12;
void dfs(int x, int y)
{
if (x == n&&m == y)
{
ans++;
return;
}
for (int i = 0; i < 2; i++){
int fx = x + co[i][0];
int fy = y + co[i][1];
if (y == 2 * x||x > n||y > m) continue;
dfs(fx, fy);
}
}
int main()
{
dfs(1, 1);
printf("%d\n",ans);
//system("pause");
return 0;
}
B题：
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#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
int ans = 0;
bool vis[20];
int num[20];
void dfs(int cnt)
{
if (cnt == 10){
int num1, num2, num3;
num1 = num2 = num3 = 0;
for (int i = 0; i < 4; i++) num1 = num1 * 10 + num[i];
if (num1>999){
for (int i = 4; i < 7; i++) num2 = num2 * 10 + num[i];
if (num2>99){
for (int i = 7; i < 10; i++) num3 = num3 * 10 + num[i];
if (num3>99 && num1 - num2 == num3) ans++, printf("%d - %d = %d\n", num1, num2, num3);
}
}
}
for (int i = 0; i < 10; i++){
if (vis[i]) continue;
vis[i] = 1;
num[cnt] = i;
dfs(cnt + 1);
vis[i] = 0;
}
}
int main()
{
dfs(0);
printf("%d\n",ans);
//system("pause");
return 0;
}
C题:
#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
const int mod = 1e9+7,mx = 2e2+10;
int c[mx][mx];
void init()
{
for (int i = 1; i < mx; i++){
c[i][0] = c[i][i] = 1;
for (int j = 1; j < i; j++)
c[i][j] = (c[i - 1][j - 1] + c[i - 1][j]) % mod;
}
}
int main()
{
init();
printf("%d\n", c[110][50]);
//system("pause");
return 0;
}
D题:
#include<iostream>
#include<algorithm>
#include<cstring>
using namespace std;
typedef long long ll;
const int co[2][2]={0,1,1,0};
const int mx = 1e5+10;
int head[mx],n,m,tot,ans;
struct node{
int y;
int nxt;
node(){}
node(int yy,int nx):y(yy),nxt(nx){}
}Edge[mx<<2];
void AddEdge(int x,int y)
{
Edge[tot] = node(y,head[x]);
head[x] = tot++;
}
bool vis[mx];
void dfs(int x)
{
if(vis[x]) return ;
vis[x] = 1;
ans++;
for(int i=head[x];~i;i=Edge[i].nxt){
int son = Edge[i].y;
if(!vis[son]) dfs(son);
}
}
int main()
{
int t,a,b;
scanf("%d",&t);
while(t--){
memset(head,-1,sizeof(head));
ans = tot = 0;
scanf("%d%d",&n,&m);
for(int i=1;i<=m;i++){
scanf("%d%d",&a,&b);
AddEdge(a,b);
AddEdge(b,a);
}
memset(vis,0,sizeof(vis));
dfs(1);
if(ans==n) puts("YES");
else puts("NO");
}
return 0;
}
\
E题:
#include<iostream>
#include<algorithm>
#include<cstring>
using namespace std;
typedef long long ll;
const int mx = 1e3+10;
int n,out[mx];
struct node{
int x,y;
node(){}
node(int xx,int yy):x(xx),y(yy){}
bool operator < (node A)const
{
if(x==A.x) return y < A.y;
return x < A.x;
}
}s[mx];
int main()
{
scanf("%d",&n);
for(int i=1;i<=n;i++) scanf("%d%d",&s[i].x,&s[i].y);
sort(s+1,s+1+n);
int ans = 0;
memset(out,0,sizeof(out));
for(int i=1;i<=n;i++){
int maxx = -20000,pos = -1;
for(int j=i-1;j>0;j--){
if(s[i].y>=s[j].y)
{
if(!out[j]&&s[j].y>maxx){
maxx = s[j].y;
pos = j;
}
}
}
if(pos!=-1) out[pos]++;
else ans++;
}
printf("%d\n",ans);
return 0;
}
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