SGU 506.Subsequences Of Substrings

求一个串S有多少子串subS满足s是subS的子序列.len(S)<=100000, len(s)<=100

直接扫一遍...

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#include<cstdio>

#include<cstring>

#include<algorithm>

 

using namespace std;

 

typedef long long ll;

 

const int maxn = 109;

 

char S[100009], s[maxn];

int Sn, sn, cnt[maxn], p;

ll ans;

 

int main() {

scanf("%s%s", S, s);

Sn = strlen(S);

sn = strlen(s);

p = 0; ans = 0;

memset(cnt, 0, sizeof cnt);

for(int i = 0; i < Sn; i++) {

for(int j = sn; j-- > 1; )

if(S[i] == s[j]) cnt[j] = max(cnt[j], cnt[j - 1]);

if(s[0] == S[i]) cnt[0] = i + 1;

if(s[sn - 1] == S[i])

ans += (ll) (cnt[sn - 1] - p) * (Sn - i), p = cnt[sn - 1];

}

printf("%lld ", ans);

return 0;

}

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506. Subsequences Of Substrings

Time limit per test: 0.5 second(s)
Memory limit: 262144 kilobytes

input: standard
output: standard

Andrew has just made a breakthrough in steganography: he realized that one can hide a message in a bigger text by making the message a subsequence of the text. We remind that a strings is called a subsequence of string t if one can remove some (possibly none) letters from t and obtain s. Andrew has prepared a text (represented by a string) with a hidden message (represented by another string which is a subsequence of the first string). But it turns out that he doesn't have enough space to write the text, so he wonders if he can remove some letters from the beginning and/or the end of his text in such a way that the hidden message still stays a subsequence of it. You should find out how many ways are there to remove some (possibly none) letters from the beginning of the given text and some (possibly none) letters from the end of the given text in such a way that the given message is a subsequence of the remaining string. Two ways are distinct if the number of letters removed from the beginning or from the end or both are distinct, even if the resulting string is the same. 

Input

The first line of the input file contains the text — a non-empty string of lowercase English letters, no more than  letters long. The second line of the input file contains the message — a non-empty string of lowercase English letters, no more than 100 letters long. It is guaranteed that the message is a subsequence of the given text. 

Output

Output one integer — the sought number of ways. 

Example(s)

sample input	sample output
abraaadabraa baa	23