A.两端1中间有几个0
#include<bits/stdc++.h>
#define INF 1e9
using namespace std;
typedef long long ll;
const int N=2e5+9;
int a[N];
inline void lan(){int n;cin>>n;ll cnt1=0;for(int i=1;i<=n;i++){cin>>a[i];cnt1+=(a[i]==1);}ll ans=0;bool ok=true;for(int i=1;i<=n;i++){if(!cnt1){break;}if(a[i]==1 && ok){cnt1--;ok=false;}else if(!ok && !a[i]){ans++;}else if(!ok && a[i]==1){cnt1--;}}cout<<ans<<'\n';
}
int main(){ios::sync_with_stdio(false);cin.tie(0),cout.tie(0);int q;cin>>q;while(q--){lan();}return 0;
}
B.记得开ll,看数组大小
贪心从最近的开始打，前缀和思想
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N=3e5+9;//数组
const int INF=1e9;
struct node{ll hp,x;
}a[N];
inline void lan(){ll n,k;cin>>n>>k;for(int i=1;i<=n;i++){cin>>a[i].hp;}for(int i=1;i<=n;i++){cin>>a[i].x;a[i].x=abs(a[i].x);//预处理}sort(a+1,a+1+n,[](const node a,const node b){return a.x<b.x;});ll cur=0;for(int i=1;i<=n;i++){cur+=a[i].hp;if(cur>a[i].x*k){cout<<"NO"<<'\n';return;}}cout<<"YES"<<'\n';
}
int main(){ios::sync_with_stdio(false);cin.tie(0),cout.tie(0);int q;cin>>q;while(q--){lan();}return 0;
}
C.
2222->1133
1111x->2222(x-4), if x>4 yes, else no
#include<bits/stdc++.h>
#define INF 1e9
using namespace std;
typedef long long ll;
const int N=3e5+9;
ll a[N],prefix[N],c[N];
bool query(int l,int r){if(l==r){return false;}ll ans=c[r]-c[l-1];ll res=prefix[r]-prefix[l-1];if(ans>res){return false;}return true;
}
inline void lan(){int n,q;cin>>n>>q;for(int i=1;i<=n;i++){cin>>a[i];a[i]--;}for(int i=1;i<=n;i++){prefix[i]=a[i]+prefix[i-1];c[i]=c[i-1]+(a[i]==0);}while(q--){int l,r;cin>>l>>r;if(query(l,r)){cout<<"YES"<<'\n';}else{cout<<"NO"<<'\n';}}cout<<'\n';
}
int main(){ios::sync_with_stdio(false);cin.tie(0),cout.tie(0);int q;cin>>q;while(q--){lan();}return 0;
}
)
