|
| 1 | +packagemedium; |
| 2 | +importjava.util.*; |
| 3 | +/** |
| 4 | + * Created by fishercoder1534 on 10/3/16. |
| 5 | + */ |
| 6 | +publicclassDecodeWays { |
| 7 | +/**Then I found this post is very concise: https://discuss.leetcode.com/topic/35840/java-clean-dp-solution-with-explanation*/ |
| 8 | +publicstaticintnumDecodings_solution2(Strings) { |
| 9 | +if(s ==null ||s.length() ==0)return0; |
| 10 | +int[]dp =newint[s.length()+1]; |
| 11 | +dp[0] =1; |
| 12 | +dp[1] = (s.charAt(0) !='0') ?1 :0; |
| 13 | +for(inti =2;i <=s.length();i++){ |
| 14 | +intfirst =Integer.valueOf(s.substring(i-1,i)); |
| 15 | +intsecond =Integer.valueOf(s.substring(i-2,i)); |
| 16 | +if(first >0 &&first <=9)dp[i] +=dp[i-1]; |
| 17 | +if(second >=10 &&second <=26)dp[i] +=dp[i-2]; |
| 18 | + } |
| 19 | +returndp[s.length()]; |
| 20 | + } |
| 21 | + |
| 22 | + |
| 23 | +/**My original accepted yet lengthy solution.*/ |
| 24 | +publicstaticintnumDecodings_solution1(Strings) { |
| 25 | + |
| 26 | +if(s ==null ||s.length() ==0)return0; |
| 27 | +Set<String>validStrings =newHashSet(); |
| 28 | +validStrings.add("1"); |
| 29 | +validStrings.add("2"); |
| 30 | +validStrings.add("3"); |
| 31 | +validStrings.add("4"); |
| 32 | +validStrings.add("5"); |
| 33 | +validStrings.add("6"); |
| 34 | +validStrings.add("7"); |
| 35 | +validStrings.add("8"); |
| 36 | +validStrings.add("9"); |
| 37 | +validStrings.add("10"); |
| 38 | +validStrings.add("11"); |
| 39 | +validStrings.add("12"); |
| 40 | +validStrings.add("13"); |
| 41 | +validStrings.add("14"); |
| 42 | +validStrings.add("15"); |
| 43 | +validStrings.add("16"); |
| 44 | +validStrings.add("17"); |
| 45 | +validStrings.add("18"); |
| 46 | +validStrings.add("19"); |
| 47 | +validStrings.add("20"); |
| 48 | +validStrings.add("21"); |
| 49 | +validStrings.add("22"); |
| 50 | +validStrings.add("23"); |
| 51 | +validStrings.add("24"); |
| 52 | +validStrings.add("25"); |
| 53 | +validStrings.add("26"); |
| 54 | + |
| 55 | +intn =s.length(); |
| 56 | +int[]dp =newint[n]; |
| 57 | +if(validStrings.contains(s.substring(0,1)))dp[0] =1; |
| 58 | +elsedp[0] =0; |
| 59 | + |
| 60 | +for(inti =1;i <n;i++){ |
| 61 | +if(validStrings.contains(s.substring(i,i+1)) &&validStrings.contains(s.substring(i-1,i+1))) { |
| 62 | +if(i >1){ |
| 63 | +dp[i] =dp[i-2] +dp[i-1]; |
| 64 | + }else { |
| 65 | +dp[1] =2; |
| 66 | + } |
| 67 | + }elseif(!validStrings.contains(s.substring(i,i+1)) && !validStrings.contains(s.substring(i-1,i+1))){ |
| 68 | +return0; |
| 69 | + }elseif(!validStrings.contains(s.substring(i,i+1)) &&validStrings.contains(s.substring(i-1,i+1))){ |
| 70 | +if(i >1)dp[i] =dp[i-2]; |
| 71 | +elsedp[i] =dp[i-1]; |
| 72 | + } |
| 73 | +elsedp[i] =dp[i-1]; |
| 74 | + } |
| 75 | + |
| 76 | +returndp[n-1]; |
| 77 | + |
| 78 | + } |
| 79 | + |
| 80 | +publicstaticvoidmain(String...args){ |
| 81 | +Stringmsg ="100"; |
| 82 | + |
| 83 | + } |
| 84 | +} |