Codeforces Round #316 (Div. 2) C. Replacement

C. Replacement

time limit per test
2 seconds

memory limit per test
256 megabytes

input
standard input

output
standard output

Daniel has a string s, consisting of lowercase English letters and period signs (characters '.').
Let's define the operation of replacementas the following sequence of steps: find a substring ".."
(two consecutive periods) in string s, of all occurrences of the substring let's choose the first one, and replace this substring with
string ".". In other words, during the replacement operation, the first two consecutive periods are replaced by one. If string s contains
no two consecutive periods, then nothing happens.

Let's define f(s) as the minimum number of operations of replacement to
perform, so that the string does not have any two consecutive periods left.

You need to process m queries, the i-th
results in that the character at position xi (1 ≤ xi ≤ n)
of string s is assigned value ci.
After each operation you have to calculate and output the value of f(s).

Help Daniel to process all queries.

Input

The first line contains two integers n and m (1 ≤ n, m ≤ 300 000)
the length of the string and the number of queries.

The second line contains string s, consisting of n lowercase
English letters and period signs.

The following m lines contain the descriptions of queries. The i-th
line contains integer xi and ci (1 ≤ xi ≤ n, ci —
a lowercas English letter or a period sign), describing the query of assigning symbol ci to
position xi.

Output

Print m numbers, one per line, the i-th
of these numbers must be equal to the value of f(s) after performing the i-th
assignment.

Sample test(s)

input

10 3
.b..bz....
1 h
3 c
9 f

output

4
3
1

input

4 4
.cc.
2 .
3 .
2 a
1 a

output

1
3
1
1

Note

Note to the first sample test (replaced periods are enclosed in square brackets).

The original string is ".b..bz....".

after the first query f(hb..bz....) =
4 ("hb[..]bz...."  →  "hb.bz[..].."  →  "hb.bz[..]."  →  "hb.bz[..]"  → "hb.bz.")

after the second query f(hbс.bz....) =
3 ("hbс.bz[..].."  →  "hbс.bz[..]."  →  "hbс.bz[..]"  →  "hbс.bz.")

after the third query f(hbс.bz..f.) =
1 ("hbс.bz[..]f."  →  "hbс.bz.f.")

Note to the second sample test.

The original string is ".cc.".

after the first query: f(..c.) =
1 ("[..]c."  →  ".c.")

after the second query: f(....) =
3 ("[..].."  →  "[..]."  →  "[..]"  →  ".")

after the third query: f(.a..) =
1 (".a[..]"  →  ".a.")

after the fourth query: f(aa..) =
1 ("aa[..]"  →  "aa.")

对于给的字符串中，每2个及以上的连续 ‘.’ ，都可以把'..' 变为‘.’，求这样操作的次数
比如 a....a 其中四个连续的'.' ，，变为 a..a 操作了2次 ，变为a.a，又操作一次，所以最后结果为3
每次输入 一个 x y 表示把串中x位置变为y ，然后查询一次结果

#include <iostream>
#include <cstdio>
#include <cstring>
#include <stdlib.h>
#include <algorithm>
#define N 300010
using namespace std;
char a
;
int main()
{
    int n,m;
    while(~scanf("%d%d",&n,&m))
    {
        scanf("%s",a);
        int len=strlen(a);
        int ans=0;
        for(int i=1;i<len;i++)
        {
            if(a[i-1] == '.' && a[i]==a[i-1])
                ans++;
        }
        for(int i=0;i<m;i++)
        {
            int x;
            char y;
            scanf("%d %c",&x,&y);
            x--;
            if(y!='.')
            {
                if(x-1>=0 && a[x-1]=='.' && a[x-1]==a[x])
                    ans--;
                if(x+1<len && a[x+1]=='.' && a[x+1]==a[x])
                    ans--;
            }
            else if(a[x]!='.')
            {
                if(x-1>=0 && a[x-1]=='.')
                    ans++;
                if(x+1<len && a[x+1]=='.')
                    ans++;
            }
             a[x]=y;
             printf("%d\n",ans);
        }
    }
    return 0;
}