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115distinctSequences.cpp
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115distinctSequences.cpp
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//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 n = s.size(), m = t.size();
vector<vector<int>>dp(n+1, vector<int>(m+1, 0));
for ( int i = 0; i <= n; i++)
{
dp[i][0] = 1;
}
for (int i = 1; i <= n; i++)
{
for (int j = 1; j <= m; j++)
{
if (s[i-1] == t[j-1])
{
dp[i][j] = dp[i-1][j-1]+dp[i-1][j];
}
else
{
dp[i][j] = dp[i-1][j];
}
}
}
return dp[n][m];
}
};