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.
这类动态规划题目就是初始化+状态转移式。要多加练习。
public class Solution { public int numDistinct(String s, String t) { int m=s.length(); int n=t.length(); int dp[][]=new int[m+1][n+1]; dp[0][0]=1; for(int i=1;i<m;i++){ dp[i][0]=1; } for(int j=1;j<n;j++){ dp[0][j]=0; } for(int i=1;i<=m;i++) for(int j=1;j<=n;j++){ if(s.charAt(i-1)==t.charAt(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]; } }
LeetCode 115:Distinct Sequence
原文：http://www.cnblogs.com/gonewithgt/p/4559974.html
