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  • Queries for Number of Palindromes(求任意子列的回文数)

    H. Queries for Number of Palindromes
    time limit per test
     5 seconds
    memory limit per test
     256 megabytes
    input
     standard input
    output
     standard output

    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.

    Sample test(s)
    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».

    代码:

    #include<stdio.h>
    #include<string.h>
    int dp[5010][5010],and1[5010][5010];
    int main()
    {
        char s[5010];
        int q,l,r,sta,end,len;
        int i;
        gets(s);
        len=strlen(s);
        for(i=0; i<len; i++)
        {
            dp[i][i]=and1[i][i]=1;
            and1[i+1][i]=1;
        }
        for(i=2;i<=len;i++)
            for(sta=0;sta<len;sta++)
            {
                end=sta+i-1;
                if(and1[sta+1][end-1]&&s[sta]==s[end])
                    and1[sta][end]=1;
                dp[sta][end]=dp[sta+1][end]+dp[sta][end-1]-dp[sta+1][end-1]+and1[sta][end];
            }
        scanf("%d",&q);
        while(q--)
        {
            scanf("%d %d",&l,&r);
            printf("%d
    ",dp[l-1][r-1]);
        }
        return 0;
    }
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  • 原文地址:https://www.cnblogs.com/jasonlixuetao/p/4531171.html
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