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Commite38f140

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update 91
1 parent34f6fd6 commite38f140

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2 files changed

+48
-0
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2 files changed

+48
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‎src/main/java/com/fishercoder/solutions/_91.java

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Original file line numberDiff line numberDiff line change
@@ -1,5 +1,8 @@
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packagecom.fishercoder.solutions;
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importjava.util.HashMap;
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importjava.util.Map;
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publicclass_91 {
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/**
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* Credit: https://discuss.leetcode.com/topic/35840/java-clean-dp-solution-with-explanation
@@ -31,4 +34,40 @@ public int numDecodings(String s) {
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returndp[s.length()];
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}
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}
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publicstaticclassSolution2 {
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/**credit: https://leetcode.com/problems/decode-ways/solution/
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* Approach 1: Recursive Approach with Memoization
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*
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* The actual code goes from the right most character to the left side to build out the dp cache map.
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* And this HashMap uses index as its key instead of a substring.
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* */
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publicintnumDecodings(Strings) {
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returndp(newHashMap<>(),s,0);
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}
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privateintdp(Map<Integer,Integer>cache,Strings,intindex) {
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if (cache.containsKey(index)) {
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returncache.get(index);
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}
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if (index ==s.length()) {
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//this means we reached the end of the string, so return 1 as success
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return1;
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}
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if (s.charAt(index) =='0') {
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//this means this string cannot be decoded
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return0;
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}
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if (index ==s.length() -1) {
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return1;
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}
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intways =dp(cache,s,index +1);
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if (Integer.parseInt(s.substring(index,index +2)) <=26) {
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ways +=dp(cache,s,index +2);
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}
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cache.put(index,ways);
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returncache.get(index);
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}
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}
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}

‎src/test/java/com/fishercoder/_91Test.java

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Original file line numberDiff line numberDiff line change
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publicclass_91Test {
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privatestatic_91.Solution1solution1;
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privatestatic_91.Solution2solution2;
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@BeforeClass
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publicstaticvoidsetup() {
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solution1 =new_91.Solution1();
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solution2 =new_91.Solution2();
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}
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@Test
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publicvoidtest1() {
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assertEquals(2,solution1.numDecodings("12"));
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assertEquals(2,solution2.numDecodings("12"));
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}
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@Test
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publicvoidtest2() {
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assertEquals(1,solution1.numDecodings("10"));
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assertEquals(1,solution2.numDecodings("10"));
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}
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}

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