Queries for Number of Palindromes(求任意子列的回文数)
5 seconds
256 megabytes
standard input
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.
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.
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.
caaaba
5
1 1
1 4
2 3
4 6
4 5
1
7
3
4
2
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[][],and1[][];
int main()
{
char s[];
int q,l,r,sta,end,len;
int i;
gets(s);
len=strlen(s);
for(i=; i<len; i++)
{
dp[i][i]=and1[i][i]=;
and1[i+][i]=;
}
for(i=;i<=len;i++)
for(sta=;sta<len;sta++)
{
end=sta+i-;
if(and1[sta+][end-]&&s[sta]==s[end])
and1[sta][end]=;
dp[sta][end]=dp[sta+][end]+dp[sta][end-]-dp[sta+][end-]+and1[sta][end];
}
scanf("%d",&q);
while(q--)
{
scanf("%d %d",&l,&r);
printf("%d\n",dp[l-][r-]);
}
return ;
}
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