leetcode-distinct sequences

Solution: when see question about two strings , DP should be considered first.

We can abstract this question to calculate appear times for string T with length i in string S with length j, which can be represented by numbers[i][j], then through observation and thinking , we can know for numbers[i][j] it should at least equal the numbers[i][j-1] and if T.charAt(i)==S.charAt(j) , numbers[i][j] should also be add numbers[i-1][j-1]

 

 class Solution
 {
 public:
     int numDistinct(string S, string T) {
         int sLen = S.length(); int tLen = T.length();
         vector<vector<int>> dp(sLen+,vector<int>(tLen+));//dp[i][j]表示对应S前i个和T前j个字符的子问题。
         for (int i = ; i <= sLen; i++) dp[i][] = ;
         for (int i = ; i <= sLen; i++)
         {
             for (int j = ; j <= tLen; j++)
             {
                 if (S[i - ] == T[j - ])
                 {
                     dp[i][j] = dp[i - ][j] + dp[i-][j-];
                 }
                 else
                 {
                     dp[i][j] = dp[i-][j];
                 }
             }
         }
         return dp[sLen][tLen];
     }
 
 };
 int main()
 {
     Solution s;
     string strS("b");
     string strT("a");
     cout << s.numDistinct(strS, strT) << endl;
     return ;
 }

http://rleetcode.blogspot.com/2014/01/distinct-subsequences-java.html