Distinct Subsequence Leetcode

Dp Learnings (27 Part Series)

1 House Robber leetcode problem
2 Jump game leetcode problem
… 23 more parts…
3 Jump game II leetcode problem
4 Cherry Pickup II Leetcode Problem
5 Partition Equals Subset Sum Leetcode problem or Subset sum equals to target
6 Maximum Sum Problem GeeksForGeeks
7 Count Palindrome Sub-Strings of a String GeeksForGeeks
8 Length of Longest Common Subsequence (LCS) and Longest common subsequence string leetcode
9 0/1 Knapsack Problem GeeksForGeeks both bounded and Unbounded
10 Shortest distance from source to all other nodes in a Directed Acyclic Graph
11 Coin change Leetcode
12 Coin Change 2 Leetcode
13 Target Sum or Partition with given difference Leetcode
14 Rod cutting Problem (similar to unbounded knapsack)
15 Length of longest common substring
16 Longest Palindromic subsequence (Same as Lcs)
17 Minimum Insertion steps needed to make a string palindrome (Same as LCS)
18 Minimum number of Insertion and deletion needed to convert String A to String B or make both the strings equal (same as lcs)
19 Shortest Common Super-sequence Leetcode (Same as Lcs string)
20 Distinct Subsequence Leetcode
21 Partition with given difference
22 Two best non overlapping events
23 Longest increasing subsequence
24 Edit distance
25 Maximum product subarray
26 Target sum
27 Maximum Multiplication Score

Given two strings s and t, return the number of distinct subsequences of s which equals t.

A string’s subsequence is a new string formed from the original string by deleting some (can be none) of the characters without disturbing the remaining characters’ relative positions. (i.e., “ACE” is a subsequence of “ABCDE” while “AEC” is not).

The test cases are generated so that the answer fits on a 32-bit signed integer.

Example 1:

Input: s = "rabbbit", t = "rabbit"
Output: 3

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Explanation:

As shown below, there are 3 ways you can generate "rabbit" from S.
rabbbit
rabbbit
rabbbit

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class Solution {
    public int numDistinct(String s, String t) {
        // we will use little bit of backtracking here 
        int dp[][] = new int[s.length()][t.length()];
        for(int row[] : dp) Arrays.fill(row, -1);
        return distinctCount(s,t,s.length()-1,t.length()-1,dp);
    }
    public int distinctCount(String s, String t, int i,int j,int dp[][]){
        //base case
        if(i=0 && j=0 && s.charAt(i)==t.charAt(j)) return 1;
        if(j<0) return 1;
        if(i<0) return 0;
        if(dp[i][j]!=-1) return dp[i][j];
        if(s.charAt(i)==t.charAt(j)){
            // so basically if its a, match , we will either reduce s and t index both or we will just reduce the index of s only.
            // in both the case we will return the sum of values that we get.
            return dp[i][j]= distinctCount(s,t,i-1,j-1,dp) + distinctCount(s,t,i-1,j,dp);
        }
        else{
            // else if its not a match we will have to reduce the s string index so 
            //as to reach to an index of s where s.charAt(i) == t.charAt(j);
            return dp[i][j] = distinctCount(s,t,i-1,j,dp);
        }
    }
}

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Dp Learnings (27 Part Series)

1 House Robber leetcode problem
2 Jump game leetcode problem
… 23 more parts…
3 Jump game II leetcode problem
4 Cherry Pickup II Leetcode Problem
5 Partition Equals Subset Sum Leetcode problem or Subset sum equals to target
6 Maximum Sum Problem GeeksForGeeks
7 Count Palindrome Sub-Strings of a String GeeksForGeeks
8 Length of Longest Common Subsequence (LCS) and Longest common subsequence string leetcode
9 0/1 Knapsack Problem GeeksForGeeks both bounded and Unbounded
10 Shortest distance from source to all other nodes in a Directed Acyclic Graph
11 Coin change Leetcode
12 Coin Change 2 Leetcode
13 Target Sum or Partition with given difference Leetcode
14 Rod cutting Problem (similar to unbounded knapsack)
15 Length of longest common substring
16 Longest Palindromic subsequence (Same as Lcs)
17 Minimum Insertion steps needed to make a string palindrome (Same as LCS)
18 Minimum number of Insertion and deletion needed to convert String A to String B or make both the strings equal (same as lcs)
19 Shortest Common Super-sequence Leetcode (Same as Lcs string)
20 Distinct Subsequence Leetcode
21 Partition with given difference
22 Two best non overlapping events
23 Longest increasing subsequence
24 Edit distance
25 Maximum product subarray
26 Target sum
27 Maximum Multiplication Score

原文链接：Distinct Subsequence Leetcode