Given a string S and a string T, count the number of distinct subsequences of T in S.
A subsequence of a string is a new string which is formed from the original string by deleting some (can be none) of the characters without disturbing the relative positions of the remaining characters. (ie, "ACE" is a subsequence of "ABCDE" while "AEC" is not).
Here is an example:
S = "rabbbit", T = "rabbit"
Return 3.
class Solution {
public:
int numDistinct(string s, string t) {
int ls = s.length(), lt = t.length(), i, j;
vector<vector<int>> dp(lt+, vector<int>(ls+, ));
for(i = ; i <= ls; i++)
dp[][i] = ;
for(i = ; i <= lt; i++)
{
for(j = i; j <= ls; j++)
{
if(t[i-] == s[j-])
{
dp[i][j] = dp[i-][j-]+dp[i][j-];
}
else
{
dp[i][j] = dp[i][j-];
}
}
}
return dp[lt][ls];
}
};
注意：
“bbb”和“”的匹配结果为1。所以第一行都为1。