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.
典型的动态规划的思想。递推公式：如果 S[i]=T[j]，dp[i][j] = dp[i - 1][j - 1] + dp[i - 1][j]， 否则dp[i][j] = dp[i - 1][j]public int numDistinct(String S, String T) { if (S == null || T == null) { return 0; } if (S.length() < T.length()) { return 0; } int lenS = S.length(); int lenT = T.length(); int[][] dp = new int[lenS + 1][lenT + 1]; for (int i = 0; i < lenS; i++) { dp[i][0] = 1; } for (int i = 1; i <= lenS; i++) { for (int j = 1; j <= lenT; j++) { dp[i][j] = dp[i - 1][j]; if(S.charAt(i-1) ==T.charAt(j-1)) { dp[i][j] += dp[i-1][j-1]; } } } return dp[lenS][lenT]; }
Distinct Subsequences,布布扣,bubuko.com
原文地址：http://blog.csdn.net/u010378705/article/details/35611267
