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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 tLen = T.length(); int sLen = S.length(); if(sLen == 0) return 0; vector<vector<int>> dp(sLen,vector<int>(tLen)); //前j+1个T字符可以有多少种S的前i+1个字符变化而来 int i=0; int j=0; if(S[0]==T[0]) dp[0][0] = 1; else dp[0][0]=0; for(i = 1; i < tLen; i++) dp[0][i]=0; for(i = 1 ; i < sLen ;i++) if(S[i]==T[0]) dp[i][0] = dp[i-1][0] + 1; else dp[i][0] = dp[i-1][0]; for(int i = 1; i < sLen ; i++) for(int j = 1; j < tLen ; j++) if(S[i]==T[j]) dp[i][j] = dp[i-1][j-1] + dp[i-1][j]; else dp[i][j] = dp[i-1][j]; return dp[sLen-1][tLen-1]; } };
115. Distinct Subsequences (String; DP)
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原文地址：http://www.cnblogs.com/qionglouyuyu/p/4922290.html
