AtCoder Beginner Contest 072

T1:
A-B B>A时输出0

#include<iostream>#include<cstdio>#include<cmath>#include<cstring>#include<algorithm>#define fo(i,a,b) for(int i=a;i<=b;i++)#define fod(i,a,b) for(int i=a;i>=b;i--)using namespace std;typedef long long ll;int main(){    ll x,t;    scanf("%lld%lld",&x,&t);    if(t>=x) cout<<"0"<<endl;    else cout<<x-t<<endl;    return 0;}

T2:

#include<iostream>#include<cstdio>#include<cmath>#include<cstring>#include<algorithm>#define fo(i,a,b) for(int i=a;i<=b;i++)#define fod(i,a,b) for(int i=a;i>=b;i--)using namespace std;typedef long long ll;const int N=1e5+10;char ch[N];int main(){    scanf("%s",ch+1);    int n=strlen(ch+1);    for(int i=1;i<=n;i+=2) {        cout<<ch[i];    }    cout<<endl;    return 0;}

T3:
记录每种可能,取最大值即可

#include<iostream>#include<cstdio>#include<cmath>#include<cstring>#include<algorithm>#define fo(i,a,b) for(int i=a;i<=b;i++)#define fod(i,a,b) for(int i=a;i>=b;i--)using namespace std;typedef long long ll;const int N=1e5+10;int ans[N],n,tot=0;int main(){    memset(ans,0,sizeof(ans));    scanf("%d",&n);    for(int x,i=1;i<=n;i++) {        scanf("%d",&x);        if(x!=0) {ans[x+1]++;ans[x]++;ans[x-1]++;}        else {ans[x]++;ans[x+1]++;tot++;}    }    int cnt=0;    fo(i,0,N-1) cnt=max(cnt,ans[i]);    cout<<cnt<<endl;    return 0;}

T4:模拟即可:

#include<iostream>#include<cstdio>#include<cmath>#include<cstring>#include<algorithm>#define fo(i,a,b) for(int i=a;i<=b;i++)#define fod(i,a,b) for(int i=a;i>=b;i--)using namespace std;const int N=1e5+10;int a[N],n,ans=0;int main(){    scanf("%d",&n);    fo(i,1,n) scanf("%d",&a[i]);    for(int i=1;i<=n;i++) {        if(a[i]==i) {            if(i==n) swap(a[i],a[i-1]);            else swap(a[i],a[i+1]);            ans++;        }    }    cout<<ans<<endl;    return 0;}