• K


    You've got a string s = s1s2... s|s| of length |s|, consisting of lowercase English letters. There also are q queries, each query is described by two integers li, ri (1 ≤ li ≤ ri ≤ |s|). The answer to the query is the number of substrings of string s[li... ri], which are palindromes.

    String s[l... r] = slsl + 1... sr (1 ≤ l ≤ r ≤ |s|) is a substring of string s = s1s2... s|s|.

    String t is called a palindrome, if it reads the same from left to right and from right to left. Formally, if t = t1t2... t|t| = t|t|t|t| - 1... t1.

    Input

    The first line contains string s (1 ≤ |s| ≤ 5000). The second line contains a single integer q (1 ≤ q ≤ 106) — the number of queries. Next q lines contain the queries. The i-th of these lines contains two space-separated integers li, ri (1 ≤ li ≤ ri ≤ |s|) — the description of the i-th query.

    It is guaranteed that the given string consists only of lowercase English letters.

    Output

    Print q integers — the answers to the queries. Print the answers in the order, in which the queries are given in the input. Separate the printed numbers by whitespaces.

    Examples

    Input
    caaaba
    5
    1 1
    1 4
    2 3
    4 6
    4 5
    Output
    1
    7
    3
    4
    2

    Note

    Consider the fourth query in the first test case. String s[4... 6] = «aba». Its palindrome substrings are: «a», «b», «a», «aba».

    题意:求一个区间内回文串的数量

    思路:要利用一个判断l~r区间的回文数组来判断这个区间是否是回文串是则为1不是则为0 然后定义一个dp数组来记录l~r区间内回文串的数量

    代码:

    #include<cstdio>
    #include<iostream>
    #include<cstring>
    #include<algorithm>
    #include<queue>
    #include<stack>
    #include<set>
    #include<vector>
    #include<map>
    #include<cmath>
    const int maxn=1e5+5;
    typedef long long ll;
    using namespace std;
    int hw[5005][5005];
    int dp[5005][5005];
    char str[5005];
    int main()
    {
       scanf("%s",str+1);
       int len=strlen(str+1);
       for(int t=1;t<=len;t++)
       {
           hw[t][t]=1;
           hw[t][t-1]=1;
           dp[t][t]=1;
       }
       for(int d=1;d<=len;d++)
       {
           for(int l=1;l+d<=len;l++)
           {
               int r=l+d;
               if(str[l]==str[r]&&hw[l+1][r-1])
               {
                   hw[l][r]=1;
            }
        }
       }
       for(int d=1;d<=len;d++)
       {
           for(int l=1;l+d<=len;l++)
           {
               int r=l+d;
               dp[l][r]=dp[l+1][r]+dp[l][r-1]-dp[l+1][r-1]+hw[l][r];
        }
       }
       int q;
       cin>>q;
       int l,r;
       while(q--)
       {
           scanf("%d%d",&l,&r);
           printf("%d
    ",dp[l][r]);
       }
       return 0; 
    }
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  • 原文地址:https://www.cnblogs.com/Staceyacm/p/11240949.html
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