acwing第30场周赛

4198. 最长合法括号子串----栈的应用

题目链接

#include 
#include 
#include 
#include 
using namespace std;
const int N = 1000100;
char s[N];
int main()
{
    scanf("%s",s+1);
    stack<int>stk;
    int n=strlen(s+1);
    int res1=0,res2=1;
    for(int i=1;i<=n;i++)
    {
        if(stk.size()&&s[i]==')'&&s[stk.top()]=='(')stk.pop();
        else stk.push(i);
        int t;
        if(stk.size())t=i-stk.top();
        else t=i;
        
        if(t>res1)res1=t,res2=1;
        else if(t&&t==res1)res2++;
        
    }
    cout<<res1<<" "<<res2<<endl;
}

3.公约数----因数分解+二分

题目链接

#include 
#include 
#include 
#include 
using namespace std;
vector<int>res;
int gcd(int a,int b)
{
    return b?gcd(b,a%b):a;
}
void div(int x)
{
    for(int i=1;i<=x/i;i++)
    {
        if(x%i==0)
        {
            res.push_back(i);
            if(i!=x/i)res.push_back(x/i);
        }
    }
}

int main()
{
    int a,b;
    cin>>a>>b;
    int d=gcd(a,b);
    div(d);
    sort(res.begin(),res.end());
    
    int m;cin>>m;
    while (m -- ){
        int L,R;
        cin>>L>>R;
        int l=0,r=res.size()-1;
        while(l<r)
        {
            int mid=l+r+1>>1;
            if(res[mid]<=R)l=mid;
            else r=mid-1;
        }
        if(res[r]<=R&&res[r]>=L)cout<<res[r]<<endl;
        else cout<<-1<<endl;
        
    }
}