Commit 2698d6d

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solves decode ways

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Original file line number	Diff line number	Diff line change
`@@ -81,6 +81,7 @@`
`81`	`81`	`\| 88 \| [Merge Sorted Array](https://leetcode.com/problems/merge-sorted-array) \| [![Java](assets/java.png)](src/MergeSortedArray.java) [![Python](assets/python.png)](python/merge_sorted_array.py) \| \|`
`82`	`82`	`\| 89 \| [Gray Code](https://leetcode.com/problems/gray-code) \| [![Java](assets/java.png)](src/GrayCode.java) \| \|`
`83`	`83`	`\| 90 \| [Subsets II](https://leetcode.com/problems/subsets-ii) \| [![Java](assets/java.png)](src/SubsetsII.java) \| \|`
	`84`	`+\| 91 \| [Decode Ways](https://leetcode.com/problems/decode-ways) \| [![Java](assets/java.png)](src/DecodeWays.java) \| \|`
`84`	`85`	`\| 94 \| [Binary Tree Inorder Traversal](https://leetcode.com/problems/binary-tree-inorder-traversal/) \| [![Java](assets/java.png)](src/BinaryTreeInorderTraversal.java) [![Python](assets/python.png)](python/binary_tree_inorder_traversal.py) \| \|`
`85`	`86`	`\| 100 \| [Same Tree](https://leetcode.com/problems/same-tree) \| [![Java](assets/java.png)](src/SameTree.java) [![Python](assets/python.png)](python/same_tree.py) \| \|`
`86`	`87`	`\| 101 \| [Symmetric Tree](https://leetcode.com/problems/symmetric-tree) \| [![Java](assets/java.png)](src/SymmetricTree.java) [![Python](assets/python.png)](python/symmetric_tree.py) \| \|`

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	`1`	`+// https://leetcode.com/problems/decode-ways`
	`2`	`+// T: O(n)`
	`3`	`+// S: O(1)`
	`4`	`+`
	`5`	`+public class DecodeWays {`
	`6`	`+ private static final char ZERO = '0';`
	`7`	`+`
	`8`	`+ public int numDecodings(String s) {`
	`9`	`+ int previous = 1, current, temp;`
	`10`	`+ current = s.charAt(s.length() - 1) > ZERO ? 1 : 0;`
	`11`	`+ for (int i = s.length() - 2 ; i >= 0 ; i--) {`
	`12`	`+ if (s.charAt(i) == ZERO) {`
	`13`	`+ previous = current;`
	`14`	`+ current = 0;`
	`15`	`+ } else {`
	`16`	`+ temp = current;`
	`17`	`+ current += isValidAlphabet(s.charAt(i), s.charAt(i + 1)) ? previous : 0;`
	`18`	`+ previous = temp;`
	`19`	`+ }`
	`20`	`+ }`
	`21`	`+ return current;`
	`22`	`+ }`
	`23`	`+`
	`24`	`+ private boolean isValidAlphabet(char a, char b) {`
	`25`	`+ return (a - ZERO) * 10 + (b - ZERO) <= 26;`
	`26`	`+ }`
	`27`	`+}`

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