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  • Distinct Subsequences

    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 l1 = s.length();
            int l2 = t.length();
            
            int dp[l1+1][l2+1];
            for(int i=0;i<l1+1;i++){
                for(int j=0;j<l2+1;j++){
                    if(i==0 && j==0){
                        dp[i][j] = 1;
                    }else if (i==0){
                        dp[i][j] = 0;
                    }else if(j==0){
                        dp[i][j] = 1;
                    }else {
                        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[l1][l2];
        }
    };
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  • 原文地址:https://www.cnblogs.com/wxquare/p/5903421.html
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