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Update decodeWays.py

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Lines changed: 16 additions & 7 deletions

Original file line number	Diff line number	Diff line change
`@@ -1,11 +1,20 @@`
	`1`	`+#first solution, O(N) time and space`
	`2`	`+class Solution(object):`
	`3`	`+ def numDecodings(self, s):`
	`4`	`+ if not s:`
	`5`	`+ return 0`
	`6`	`+ dp = [0]*(len(s)+1)`
	`7`	`+ dp[0] = 1`
	`8`	`+ for i in range(1, len(s)+1):`
	`9`	`+ if s[i-1] != '0':`
	`10`	`+ dp[i] += dp[i-1]`
	`11`	`+ if i != 1:`
	`12`	`+ if int(s[i-2:i]) in range(10, 27):`
	`13`	`+ dp[i] += dp[i-2]`
	`14`	`+ return dp[len(s)]`
`1`	`15`
`2`		`-`
`3`		`-`
`4`		`-`
`5`		`-`
`6`		`-`
`7`		`-`
`8`		`-O(N) time, O(1) space DP via "general fibonacci numbers"`
	`16`	`+`
	`17`	`+#O(N) time, O(1) space DP via "general fibonacci numbers"`
`9`	`18`	`class Solution(object):`
`10`	`19`	`def numDecodings(self, s):`
`11`	`20`	`if len(s) == 0 or s[0] == '0':`

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