CodeForces 570B，C

男娘i 2022-08-18 14:21 18阅读 0赞

[CodeForces 570B][]

题意：给定n和m，然后再（1-n）中随机取出c，求一个m使得 ![5542979dae766ee1599c2141e6761418][] 的概率最大，概率一样时输出最小的m。

思路：只需要看1到m-1和m+1和n的最大的那一边就可以了，坑是n=1的情况和n为奇数m为n/2+1的情况要特判。

code：

#include <iostream>
    #include <cstdio>
    #include <cmath>
    #include <algorithm>
    #include <cstring>
    #include <sstream>
    #include <string>
    #include <vector>
    #include <list>
    #include <queue>
    #include <stack>
    #include <map>
    #include <set>
    #include <bitset>
    
    using namespace std;
    
    typedef long long ll;
    typedef unsigned long long ull;
    typedef long double ld;
    
    const int INF=0x3fffffff;
    const int inf=-INF;
    const int N=1e5+5;
    const int M=2005;
    const int mod=1000000007;
    const double pi=acos(-1.0);
    
    #define cls(x,c) memset(x,c,sizeof(x))
    #define cpy(x,a) memcpy(x,a,sizeof(a))
    #define ft(i,s,n) for (int i=s;i<=n;i++)
    #define frt(i,s,n) for (int i=s;i>=n;i--)
    #define lson l,m,rt<<1
    #define rson m+1,r,rt<<1|1
    #define lrt  rt<<1
    #define rrt  rt<<1|1
    #define middle int m=(r+l)>>1
    #define lowbit(x) (x&-x)
    #define pii pair<int,int>
    #define mk make_pair
    #define IN freopen("in.txt","r",stdin);
    #define OUT freopen("out.txt","w",stdout);
    
    int main()
    {
        int n,m;
        scanf("%d %d",&n,&m);
        if (n==1) puts("1");
        else {
            if (m-1>n-m) printf("%d\n",m-1);
            else if (n%2==1&&m==n/2+1) printf("%d\n",m-1);
            else printf("%d\n",m+1);
        }
    }

[CodeForces 570][CodeForces 570B]C

题意：给定一个n的字符的字符串，然后有m个修改，对于每次修改，询问字符串中有连续。。的个数。

思路：一开始先统计一下个数，然后对于每次修改，最多可修改2个个数。然后分情况讨论就可以。

code：

#include <iostream>
    #include <cstdio>
    #include <cmath>
    #include <algorithm>
    #include <cstring>
    #include <sstream>
    #include <string>
    #include <vector>
    #include <list>
    #include <queue>
    #include <stack>
    #include <map>
    #include <set>
    #include <bitset>
    
    using namespace std;
    
    typedef long long ll;
    typedef unsigned long long ull;
    typedef long double ld;
    
    const int INF=0x3fffffff;
    const int inf=-INF;
    const int N=3e5+5;
    const int M=2005;
    const int mod=1000000007;
    const double pi=acos(-1.0);
    
    #define cls(x,c) memset(x,c,sizeof(x))
    #define cpy(x,a) memcpy(x,a,sizeof(a))
    #define ft(i,s,n) for (int i=s;i<=n;i++)
    #define frt(i,s,n) for (int i=s;i>=n;i--)
    #define lson l,m,rt<<1
    #define rson m+1,r,rt<<1|1
    #define lrt  rt<<1
    #define rrt  rt<<1|1
    #define middle int m=(r+l)>>1
    #define lowbit(x) (x&-x)
    #define pii pair<int,int>
    #define mk make_pair
    #define IN freopen("in.txt","r",stdin);
    #define OUT freopen("out.txt","w",stdout);
    char s[N];
    int sol(int p,int c){
        if (c=='.'&&s[p]!='.'){
            s[p]=c;
            if (s[p-1]=='.'&&s[p+1]=='.') return 2;
            if (s[p-1]=='.'||s[p+1]=='.') return 1;
            return 0;
        }
        if (c!='.'&&s[p]=='.'){
            s[p]=c;
            if (s[p-1]=='.'&&s[p+1]=='.') return -2;
            if (s[p-1]=='.'||s[p+1]=='.') return -1;
            return 0;
        }
        return 0;
    }
    int main()
    {
        int n,k,p,t=0;
        scanf("%d %d",&n,&k);
        scanf("%s",s+1);s[0]='#';
        ft(i,1,n) if(s[i]=='.'&&s[i-1]=='.') t++;
        ft(i,1,k){
            char ch[2];
            scanf("%d %s",&p,&ch);
            t+=sol(p,ch[0]);
            printf("%d\n",t);
        }
    }

[CodeForces 570B]: http://acm.hust.edu.cn/vjudge/problem/visitOriginUrl.action?id=222307
[5542979dae766ee1599c2141e6761418]: http://7xjob4.com1.z0.glb.clouddn.com/5542979dae766ee1599c2141e6761418