Another Meaning

链接：http://acm.hust.edu.cn/vjudge/problem/435534/origin

题目：As is known to all, in many cases, a word has two meanings. Such as “hehe”, which not only means “hehe”, but also means “excuse me”.
Today, ?? is chating with MeiZi online, MeiZi sends a sentence A to ??. ?? is so smart that he knows the word B in the sentence has two meanings. He wants to know how many kinds of meanings MeiZi can express.

题意：字符串a中出现的b可以被修改（理解成换成*比较方便），当然可以不修改。问共有多少种方案。

分析：一开始想用贪心的，但是情况太复杂（出现b的一部分和a链接后还可以匹配等）不太好讨论，所以采用dp，把问题分解成从1到n，n《=a的长度，的字符可以有多少方案，再之后的b的长度的字符串是否可以替换，可以就是(n+len(b)-1)位的种数（因为长度不够，没达到替换要求，视为不替换的方案数）加上替换后的n的种数（替换为*）。最后dp【len（a）】即为结果。（对了，由于是字串是动态的，不能用kmp优化，要用哈希来优化，不知道暴力匹配会不会超时。。。。）

题解：

#include <iostream>#include <cstdio>#include <cstdlib>#include <algorithm>#include <queue>#include <stack>#include <vector>#include <map>#include <string>#include <cstring>#include <functional>#include <cmath>#include <cctype>#include <cfloat>#include <climits>#include <complex>#include <deque>#include <list>#include <set>#include <utility>#define rt return#define fr freopen("in.txt","r",stdin)#define fw freopen("out.txt","w",stdout)#define ll long long#define ull unsigned long long#define detie ios_base::sync_with_stdio(false);cin.tie(false);cout.tie(false)#define pii pair<int,int>#define lowbit(x) x&(-x)using namespace std;#define maxi 0x3f3f3f3f#define MAX 100020int t, dp[MAX], al, bl, cases;char a[MAX], b[MAX];ull B = 100000007;ull MOD = 1000000007;int main(){//fr;detie;cin >> t;while (t--){cin >> a >> b;al = strlen(a);bl = strlen(b);ull ah = 0, bh = 0, t = 1;for (int i = 0; i < bl; i++){t *= B;ah = ah*B + a[i];bh = bh*B + b[i];}memset(dp, 0, sizeof dp);fill(dp, dp + bl, 1);for (int i = 0; i + bl <= al; i++){dp[i + bl] = dp[i + bl - 1];if (ah == bh)dp[i + bl] = (dp[i + bl] + dp[i]) % MOD;if (i + bl < al)ah = ah*B + a[i + bl] - t*a[i];}printf("Case #%d: %d\n", ++cases, dp[al]);}rt 0;}