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@@ -1,10 +1,30 @@
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package main
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func numDistinct(s string, t string) int {
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- return 0
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+ m, n := len(s), len(t)
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+ if m < n {
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+ return 0
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+ }
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+ dp := make([][]int, m+1) // dp[i, j] means num distinct between s[0...i-1] and t[0...j-1]
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+ for i := range dp {
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+ dp[i] = make([]int, n+1)
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+ dp[i][0] = 1
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+ }
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+ // if s[i-1] == t[i-1], dp[i, j] = dp[i-1, j-1] + dp[i-1, j]
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+ // else dp[i, j] = dp[i-1, j]
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+ for i := 1; i <= m; i++ {
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+ for j := 1; j <= n && j <= i; j++ {
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+ if s[i-1] == t[j-1] {
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+ dp[i][j] = dp[i-1][j-1] + dp[i-1][j]
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+ } else {
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+ dp[i][j] = dp[i-1][j]
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+ }
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+ }
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+ }
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+ return dp[m][n]
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}
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-func main() {
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- println(numDistinct("rabbbit", "rabbit"), 3)
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- println(numDistinct("babgbag", "bag"), 5)
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-}
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+// func main() {
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+// println(numDistinct("rabbbit", "rabbit"), 3)
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+// println(numDistinct("babgbag", "bag"), 5)
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+// }
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