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uva 10069
Problem E
Distinct Subsequences
Input: standard input<style=‘mso-bidi-font-weight:normal‘>
Output: standard output
A subsequence of a given sequence is just the given sequence with some elements (possibly none) left out. Formally, given a sequenceX=x1x2…xm, another sequence Z=z1z2…zk is a subsequence of X if there exists a strictly increasing sequence <i1, i2, …, ik> of indices of X such that for all j = 1, 2, …, k, we have xij=zj. For example, Z=bcdb is a subsequence of X=abcbdab with corresponding index sequence < 2, 3, 5, 7 >.
In this problem your job is to write a program that counts the number of occurrences of Z in X as a subsequence such that each has a distinct index sequence.
Input
The first line of the input contains an integer N indicating the number of test cases to follow.
The first line of each test case contains a string X, composed entirely of lowercase alphabetic characters and having length no greater than 10,000. The second line contains another string Z having length no greater than 100 and also composed of only lowercase alphabetic characters. Be assured that neither Z nor any prefix or suffix of Z will have more than 10100 distinct occurrences in X as a subsequence.
Output
For each test case in the input output the number of distinct occurrences of Z in X as a subsequence. Output for each input set must be on a separate line.
Sample Input
2babgbag
bag
rabbbit
rabbit
Sample Output
53
____________________________________________________________________________________
Rezaul Alam Chowdhury
解题报告:
dp[i][j]表示:b的前i个字符在a的前ij个字符中出现的次数。
如果a[i] == b[j]则 dp[i][j] = dp[ii][ji-1] + dp[i-1][j-1]
如果a[i] != b[j]则 dp[i][j] = dp[i][j-1]
#include <iostream>#include <cstdio>#include <cstdlib>#include <cstring>#include <string>#include <algorithm>using namespace std;const int MAXN = 110; //数组越大,时间复杂度越高啊,谨慎使用。 char X[10010], Y[110];struct bign{ int len, s[MAXN]; bign() { memset(s, 0, sizeof(s)); len = 1; } bign operator = (const char *num) { len = strlen(num); for(int i = 0; i < len; i++) s[i] = num[len-i-1] - ‘0‘; return *this; } bign operator = (const int num) { char s[MAXN]; sprintf(s, "%d", num); *this = s; return *this; } bign (int num) { *this = num;} bign (char *num) { *this = num;} bign operator + (const bign &b) { bign c; c.len = 0; for(int i = 0, g = 0; g || i < max(len, b.len); i++) { int x = g; if(i < len) x += s[i]; if(i < b.len) x += b.s[i]; c.s[c.len++] = x % 10; g = x / 10; } return c; } bign operator - (const bign &b) { bign c; c.len = 0; for(int i = 0; i < max(len, b.len); i++) { c.s[i] += s[i]-b.s[i]; if(c.s[i] < 0) { c.s[i] += 10; c.s[i+1]--; } } while(c.s[len-1] == 0 && len > 1) len--; c.len = len; return c; } bign operator += (const bign &b) { *this = *this + b; return *this; } string str() const { string res = ""; for(int i = 0; i < len; i++) res = char(s[i] + ‘0‘) + res; if(res == "") res = "0"; return res; }}d[110][10010];istream& operator >> (istream& in, bign &x){ string s; in >> s; x = s.c_str(); return in;}ostream& operator << (ostream& out, bign &x){ out << x.str(); return out;}void solve(){ scanf("%s%s", X+1, Y+1); int lenX = strlen(X+1), lenY = strlen(Y+1); for(int i = 0; i <= lenX; i++) d[0][i] = 1; for(int i = 1; i <= lenY; i++) { for(int j = i; j <= lenX; j++) { d[i][j] = d[i][j-1]; if(Y[i] == X[j]) d[i][j] += d[i-1][j-1]; } } cout<<d[lenY][lenX]<<endl;}int main(){ int T; scanf("%d", &T); while(T--) { solve(); } return 0;}
uva 10069