115 ut pass

Author: aQua

Algorithms/0115.distinct-subsequences/distinct-subsequences.go

@@ -2,13 +2,6 @@ package Problem0115
 
 func numDistinct(s string, t string) int {
 	m, n := len(s), len(t)
-	if m < n {
-		return 0
-	}
-
-	if n == 0 {
-		return 1
-	}
 
 	dp := make([][]int, m+1)
 	for i := 0; i <= m; i++ {
@@ -17,11 +10,7 @@ func numDistinct(s string, t string) int {
 	}
 
 	for j := 1; j <= n; j++ {
-		if s[:j] == t[:j] {
-			dp[j][j] = 1
-		}
-
-		for i := j + 1; i <= m; i++ {
+		for i := j; i <= m; i++ {
 			if n-j <= m-i && s[i-1] == t[j-1] {
 				dp[i][j] = dp[i-1][j-1] + dp[i-1][j]
 			} else {
@@ -30,5 +19,6 @@ func numDistinct(s string, t string) int {
 
 		}
 	}
+
 	return dp[m][n]
 }

Algorithms/0115.distinct-subsequences/distinct-subsequences_test.go

@@ -17,6 +17,12 @@ func Test_Problem0115(t *testing.T) {
 		ans int
 	}{
 
+		{
+			"aaaaaa",
+			"",
+			1,
+		},
+
 		{
 			"aaaaaa",
 			"aa",