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 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 570C
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);}
}
