feat:add Solution.cpp for 0115. Distinct Subsequences

Author: Stackingrule

solution/0100-0199/0115.Distinct Subsequences/Solution.cpp

@@ -0,0 +1,14 @@
+class Solution {
+public:
+    int numDistinct(string s, string t) {
+        int m = s.size(), n = t.size();
+        vector<vector<long>> dp(n + 1, vector<long>(m + 1));
+        for (int j = 0; j <= m; ++j) dp[0][j] = 1;
+        for (int i = 1; i <= n; ++i) {
+            for (int j = 1; j <= m; ++j) {
+                dp[i][j] = dp[i][j - 1] + (t[i - 1] == s[j - 1] ? dp[i - 1][j - 1] : 0);
+            }
+        }
+        return dp[n][m];
+    }
+};