水题一道,不过我为什么要将她记录下来呢,在wa了无数次后,我胡乱的吧输入同步(#define IOS ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);)取消掉了,结果就ac了,看来以后还是打scanfprintf好,不能再偷懒了。
#include <bits/stdc++.h>
#define fi first
#define se second
#define INF 0x3f3f3f3f
#define ll long long
#define ld long double
#define mem(ar,num) memset(ar,num,sizeof(ar))
#define me(ar) memset(ar,0,sizeof(ar))
#define lowbit(x) (x&(-x))
#define IOS ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define DEBUG cout<<endl<<"DEBUG"<<endl;
using namespace std;
typedef pair<int, int> pii;
const int maxn = 3e5 + 200;
int n, m, y[1000010];
char c, s[1000010];
int main() {
int t;
cin >> t;
while(t--) {
me(y);
int ans = 0, bu = 0, k = 0;
scanf("%d %d", &n, &m);
scanf("%s", s);
k = n;
if(n & 1)
k = n, y[n / 2] = 0, n--;
for(int i = 0; i < n / 2; i++) {
if(s[i] != s[k - 1 - i]) {
y[i] = y[k - 1 - i] = 1, bu++;
} else
y[i] = y[k - 1 - i] = 0;
}
for(int i = 1, x; i <= m; i++) {
char ch[2];
scanf("%d %s", &x, ch);
s[--x] = ch[0];
if((k & 1) && x == k / 2) {
if(!bu) {
ans++;
}
continue;
}
if(y[x] == 1 && s[x] == s[k - 1 - x]) {
y[x] = y[k - 1 - x] = 0;
bu--;
} else if(s[x] != s[k - 1 - x] && y[x] == 0) {
y[x] = y[k - 1 - x] = 1;
bu++;
}
if(!bu) {
ans++;
}
}
printf("%d\n", ans);
}
return 0;
}