题目链接:http://codeforces.com/contest/1155
第一题(模拟)
#include<bits/stdc++.h>
using namespace std;#define debug puts("YES");
#define rep(x,y,z) for(int (x)=(y);(x)<(z);(x)++)
#define ll long long#define lrt int l,int r,int rt
#define lson l,mid,rt<<1
#define rson mid+1,r,rt<<1|1
#define root l,r,rt
#define mst(a,b) memset((a),(b),sizeof(a))
#define pii pair<int,int>
#define fi first
#define se second
#define mk(x,y) make_pair(x,y)
const int mod=1e9+7;
const int maxn=5e2+10;
const int ub=1e6;
ll powmod(ll x,ll y){ll t; for(t=1;y;y>>=1,x=x*x%mod) if(y&1) t=t*x%mod; return t;}
int gcd(int x,int y){if(y==0) return x;return gcd(y,x%y);
}string s;
int n;int main(){cin>>n>>s;int flag=0,l,r;///int len=s.size();for(int i=0;i<n-1;i++){if(s[i]>s[i+1]){l=i,r=i+1;flag=1;break;}}if(flag==0) puts("NO");else {puts("YES");cout<<l+1<<" "<<r+1<<endl;}return 0;
}第二题(博弈+模拟)
#include<bits/stdc++.h>
using namespace std;#define debug puts("YES");
#define rep(x,y,z) for(int (x)=(y);(x)<(z);(x)++)
#define ll long long#define lrt int l,int r,int rt
#define lson l,mid,rt<<1
#define rson mid+1,r,rt<<1|1
#define root l,r,rt
#define mst(a,b) memset((a),(b),sizeof(a))
#define pii pair<int,int>
#define fi first
#define se second
#define mk(x,y) make_pair(x,y)
const int mod=1e9+7;
const int maxn=5e2+10;
const int ub=1e6;
ll powmod(ll x,ll y){ll t; for(t=1;y;y>>=1,x=x*x%mod) if(y&1) t=t*x%mod; return t;}
int gcd(int x,int y){if(y==0) return x;return gcd(y,x%y);
}
int flag=0,n;
string s;
int main(){cin>>n>>s;int cnt=(n-11)/2,stp=cnt;for(int i=0;i<n;i++){if(s[i]=='8') flag++;}if(flag<=cnt){puts("NO");}else{int isw=1;for(int i=0;i<n;i++) if(s[i]=='8'){cnt--;if(cnt==-1){if(i-stp>stp) isw=0;break;}}if(isw) puts("YES");else puts("NO");}return 0;
}第三题(数论)
#include<bits/stdc++.h>
using namespace std;#define debug puts("YES");
#define rep(x,y,z) for(int (x)=(y);(x)<(z);(x)++)
#define ll long long#define lrt int l,int r,int rt
#define lson l,mid,rt<<1
#define rson mid+1,r,rt<<1|1
#define root l,r,rt
#define mst(a,b) memset((a),(b),sizeof(a))
#define pii pair<int,int>
#define fi first
#define se second
#define mk(x,y) make_pair(x,y)
const int mod=1e9+7;
const int maxn=3e5+10;
const int ub=1e6;
ll powmod(ll x,ll y){ll t; for(t=1;y;y>>=1,x=x*x%mod) if(y&1) t=t*x%mod; return t;}
ll gcd(ll x,ll y){if(y==0) return x;return gcd(y,x%y);
}
ll n,m;
ll a[maxn],b[maxn];
int main(){cin>>n>>m;ll gd=0;rep(i,0,n){cin>>a[i];///gd1=gcd(gd1,a[i]);if(i) gd=gcd(gd,a[i]-a[i-1]);}int flag=0,res=0,pos=0;rep(i,0,m){cin>>b[i];if(gd%b[i]==0){flag=1;res=i+1;pos=a[0];}}if(flag){puts("YES");cout<<a[0]<<" "<<res<<endl;}else{puts("NO");}return 0;
}第四题(DP):
#include<bits/stdc++.h>
using namespace std;#define debug puts("YES");
#define rep(x,y,z) for(int (x)=(y);(x)<(z);(x)++)
#define ll long long#define lrt int l,int r,int rt
#define lson l,mid,rt<<1
#define rson mid+1,r,rt<<1|1
#define root l,r,rt
#define mst(a,b) memset((a),(b),sizeof(a))
#define pii pair<int,int>
#define fi first
#define se second
#define mk(x,y) make_pair(x,y)
const int mod=1e9+7;
const int maxn=3e5+100;
const int ub=1e6;
ll powmod(ll x,ll y){ll t; for(t=1;y;y>>=1,x=x*x%mod) if(y&1) t=t*x%mod; return t;}
ll gcd(ll x,ll y){if(y==0) return x;return gcd(y,x%y);
}
ll n,x,k;
ll dp[maxn][3];
int main(){cin>>n>>k;mst(dp,0);ll ans=0;rep(i,1,n+1){cin>>x;dp[i][0]=dp[i-1][0]+x;dp[i][0]=max(dp[i][0],0LL);dp[i][1]=max(dp[i-1][1],dp[i-1][0])+x*k;dp[i][1]=max(dp[i][1],0LL);dp[i][2]=max(dp[i-1][1],dp[i-1][2])+x;dp[i][2]=max(dp[i][2],0LL);ans=max(ans,max(dp[i][2],max(dp[i][0],dp[i][1])));}cout<<ans<<"\n";return 0;
}