[CF245H] Queries for Number of Palindromes (容斥原理dp计数)

 1 #include <cstdio>
 2 #include <cstring>
 3 #include <algorithm>
 4 #include <vector>
 5 #include <map>
 6 #include <set>
 7 #include <bitset>
 8 #include <cmath>
 9 #include <numeric>
10 #include <iterator>
11 #include <iostream>
12 #include <cstdlib>
13 #include <functional>
14 #include <queue>
15 #include <stack>
16 #include <string>
17 using namespace std;
18 #define PB push_back
19 #define MP make_pair
20 #define SZ size()
21 #define ST begin()
22 #define ED end()
23 #define CLR clear()
24 #define ZERO(x) memset((x),0,sizeof(x))
25 typedef long long LL;
26 typedef unsigned long long ULL;
27 typedef pair<int,int> PII;
28 const double EPS = 1e-8;
29 
30 const int MAX_N = 5555;
31 char str[MAX_N];
32 int dp[MAX_N][MAX_N];
33 int q;
34 
35 bool IsPalindromes(int i,int j){
36     if(i>=j) return true;
37     return dp[i][j] == dp[i+1][j]+dp[i][j-1]-dp[i+1][j-1]+1;
38 }
39 
40 int main() {
41     scanf("%s",str+1);
42     int length = strlen(str+1);
43 //    printf("length: %d\n",length);
44     for(int i=1;i<=length;i++) dp[i][i] = 1;
45     
46     for(int len = 2; len<=length; len++) {
47         for(int i=1;i<=length;i++) {
48             int j = i+len-1;
49             if( j>length ) continue;
50             dp[i][j] = dp[i][j-1]+dp[i+1][j]-dp[i+1][j-1];
51             if( str[i]==str[j] ) {
52                 if( IsPalindromes(i+1,j-1) ) {
53                     dp[i][j] ++ ;
54                 }
55             }
56         }
57     }
58     
59 //    for(int i=1;i<=length;i++) {
60 //        for(int j=1;j<=length;j++) {
61 //            printf("%d ",dp[i][j]);
62 //        }
63 //        puts("");
64 //    }
65     
66     scanf("%d",&q);
67     
68     while( q-- ) {
69         int l,r;
70         scanf("%d%d",&l,&r);
71         printf("%d\n",dp[l][r]);
72     }
73     
74     return 0;
75 }