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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. typedef long long ll;
  5.  
  6. const int N = 1e5 + 1;
  7. char s[N];
  8.  
  9. int main(int argc, char **argv) {
  10. 	int T;
  11. 	scanf("%d", &T);
  12. 	while (T-- != 0) {
  13. 		int n, m;
  14. 		scanf("%d%d%s", &n, &m, s);
  15. 		int ok = 0, need = (n + 1) >> 1;
  16. 		for (int i = 0; i * 2 < n; ++i)
  17. 			if (s[i] == s[n - i - 1])
  18. 				++ok;
  19. 		int res = 0, p;
  20. 		char c;
  21. 		for (int i = 0; i < m; ++i) {
  22. 			scanf("%d %c", &p, &c);
  23. 			--p;
  24. 			if (p != n - p - 1 && s[p] != s[n - p - 1] && s[n - p - 1] == c)
  25. 				++ok;
  26. 			if (p != n - p - 1 && s[p] == s[n - p - 1] && s[n - p - 1] != c)
  27. 				--ok;
  28. 			s[p] = c;
  29. 			if (ok == need)
  30. 				++res;
  31. 		}
  32. 		printf("%d\n", res);
  33. 	}
  34. 	return 0;
  35. }
Success #stdin #stdout 0s 4516KB
comments (?)
stdin
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1
10 7
abcdefdcba
5 x
6 x
4 d
2 d
3 y
8 y
9 d
stdout
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3
https://ideone.com/YYrF7f
language:
C++14 (gcc 8.3)
created:
6 years ago
visibility:
secret

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