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DistinctSubsequence.cpp
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38 lines (31 loc) · 1.04 KB
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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 m = S.length();
int n = T.length();
if (m <n) return 0;
vector<vector<int> > dp(m+1, vector<int>(n+1, 0));
for (int i = 0; i <= m; ++i) dp[i][0] = 1;
for (int i =1; i <=m; ++i) {
for (int j =1; j <=n; ++j) {
if (S[i-1] == T[j-1]) {
dp[i][j] = dp[i-1][j] + dp[i-1][j-1];
}
else {
dp[i][j] = dp[i-1][j];
}
}
}
return dp[m][n]; //note here we return m,n
}
};