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main_review_1_150.go
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/
main_review_1_150.go
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package main
func main() {}
// 由注释得将t反序计算一样的
func numDistinct(s string, t string) int {
dp := make([]int, len(t)+1)
// 默认就是 0
// for i := range dp {
// dp[i] = 0
// }
dp[0] = 1
for sIndex := 0; sIndex < len(s); sIndex++ {
for tIndex := len(t) - 1; tIndex >= 0; tIndex-- {
if s[sIndex] == t[tIndex] {
dp[tIndex+1] += dp[tIndex]
}
}
}
return dp[len(t)]
}
// r a b b b i t
// 1 1 1 1 1 1 1 1
// r 0 1 |
// a 0 0 v
// b 0 2(3,4)
// b 0 1(4,4) ?(4,5)
// 使用 s[5]的 b 则从s[0:5]中找一个'b', 即sequence 'rb', 则等于dp(3,4) == 2
// 不使用 s[5] b 则从s[0:5]中找俩个'b'即 'rabb' 等于dp(4,4) == 1
func numDistinct1(s string, t string) int {
dp := make([]int, len(t)+1)
for index := range dp {
dp[index] = 0
}
for sIndex := 0; sIndex < len(s); sIndex++ {
pre := 1
for tIndex := 0; tIndex < len(t); tIndex++ {
temp := dp[tIndex+1]
if s[sIndex] == t[tIndex] {
dp[tIndex+1] = dp[tIndex+1] + pre
}
pre = temp
}
}
return dp[len(t)]
}