An impassioned circulation of affection（尺取+预处理）

 1 #include <set>
 2 #include <map>
 3 #include <queue>
 4 #include <stack>
 5 #include <cmath>
 6 #include <bitset>
 7 #include <cstdio>
 8 #include <string>
 9 #include <vector>
10 #include <cstdlib>
11 #include <cstring>
12 #include <iostream>
13 #include <algorithm>
14 using namespace std;
15 
16 typedef long long ll;
17 typedef pair<ll, ll> pll;
18 typedef pair<ll, int> pli;
19 typedef pair<int, ll> pil;;
20 typedef pair<int, int> pii;
21 typedef unsigned long long ull;
22 
23 #define lson i<<1
24 #define rson i<<1|1
25 #define bug printf("*********\n");
26 #define FIN freopen("D://code//in.txt", "r", stdin);
27 #define debug(x) cout<<"["<<x<<"]" <<endl;
28 #define IO ios::sync_with_stdio(false),cin.tie(0);
29 
30 const double eps = 1e-8;
31 const int mod = 1000000007;
32 const int maxn = 1500 + 7;
33 const double pi = acos(-1);
34 const int inf = 0x3f3f3f3f;
35 const ll INF = 0x3f3f3f3f3f3f3f;
36 
37 int n, q, x, cnt;
38 char s[maxn], c[5];
39 int ans[26][maxn];
40 
41 int main() {
42     //FIN;
43     scanf("%d%s", &n, s);
44     for(int i = 0; i < 26; i++) {
45         for(int j = 0; j < n; j++) {
46             cnt = 0;
47             for(int k = j; k < n; k++) {
48                 if(s[k] != ‘a‘ + i) cnt++;
49                 ans[i][cnt] = max(ans[i][cnt], k - j + 1);
50             }
51         }
52         for(int j = 1; j <= n; j++) {
53             ans[i][j] = max(ans[i][j], ans[i][j-1]);
54         }
55     }
56     scanf("%d", &q);
57     while(q--) {
58         scanf("%d%s", &x, c);
59         int num = c[0] - ‘a‘;
60         printf("%d\n", ans[num][x]);
61     }
62     return 0;
63 }