|
| 1 | +/* |
| 2 | +* KMP algorithm |
| 3 | +*/ |
| 4 | +classSolution { |
| 5 | +funstrStr(haystack:String,needle:String):Int { |
| 6 | +if(needle=="")return0 |
| 7 | + |
| 8 | +val lps=IntArray(needle.length) |
| 9 | +var prevLPS=0 |
| 10 | +var i=1 |
| 11 | +while(i< needle.length) { |
| 12 | +if(needle[i]== needle[prevLPS]) { |
| 13 | + lps[i]= prevLPS+1 |
| 14 | + prevLPS++ |
| 15 | + i++ |
| 16 | + }elseif(prevLPS==0) { |
| 17 | + lps[i]=0 |
| 18 | + i++ |
| 19 | + }else{ |
| 20 | + prevLPS= lps[prevLPS-1] |
| 21 | + } |
| 22 | + } |
| 23 | + |
| 24 | + i=0 |
| 25 | +var j=0 |
| 26 | +while (i< haystack.length) { |
| 27 | +if(haystack[i]== needle[j]){ |
| 28 | + i++ |
| 29 | + j++ |
| 30 | + }elseif(j==0){ |
| 31 | + i++ |
| 32 | + }else{ |
| 33 | + j= lps[j-1] |
| 34 | + } |
| 35 | +if(j== needle.length) { |
| 36 | +return i- needle.length |
| 37 | + } |
| 38 | + } |
| 39 | + |
| 40 | +return-1 |
| 41 | + } |
| 42 | +} |
| 43 | + |
| 44 | +/* |
| 45 | +* Rabin-Karp string hashing with bad hash |
| 46 | +*/ |
| 47 | +classSolution { |
| 48 | +funstrStr(haystack:String,needle:String):Int { |
| 49 | +if(needle.length> haystack.length)return-1 |
| 50 | + |
| 51 | +var needleHash=0 |
| 52 | +var hayHash=0 |
| 53 | + |
| 54 | +for(iin0..needle.lastIndex) { |
| 55 | + needleHash+= needle[i]-'a' |
| 56 | + hayHash+= haystack[i]-'a' |
| 57 | + } |
| 58 | + |
| 59 | +for(iin0..(haystack.length- needle.length)) { |
| 60 | +if(hayHash== needleHash) { |
| 61 | +for(jin0..needle.lastIndex) { |
| 62 | +if(haystack[i+ j]!= needle[j]) |
| 63 | +break |
| 64 | +if(j== needle.lastIndex) |
| 65 | +return i |
| 66 | + } |
| 67 | + } |
| 68 | +if(i== haystack.length- needle.length) |
| 69 | +break |
| 70 | + hayHash-= haystack[i]-'a' |
| 71 | + hayHash+= haystack[i+ needle.length]-'a' |
| 72 | + } |
| 73 | + |
| 74 | +return-1 |
| 75 | + } |
| 76 | +} |
| 77 | + |
| 78 | +/* |
| 79 | +* Using Trie to match pattern |
| 80 | +*/ |
| 81 | +classTrieNode() { |
| 82 | +val child= arrayOfNulls<TrieNode>(26) |
| 83 | +var isEnd=false |
| 84 | +} |
| 85 | + |
| 86 | +classSolution { |
| 87 | +funstrStr(haystack:String,needle:String):Int { |
| 88 | +if(needle=="")return0 |
| 89 | + |
| 90 | +var root:TrieNode?=TrieNode() |
| 91 | + |
| 92 | +var current= root |
| 93 | +for(cin needle){ |
| 94 | +if(current?.child?.get(c-'a')==null) |
| 95 | + current?.child?.set(c-'a',TrieNode()) |
| 96 | + current= current?.child?.get(c-'a') |
| 97 | + } |
| 98 | + current?.isEnd=true |
| 99 | + |
| 100 | +var i=0 |
| 101 | +while(i< haystack.length+1- needle.length) { |
| 102 | + current= root?.child?.get(haystack[i]-'a') |
| 103 | +var j= i |
| 104 | +while(current!=null) { |
| 105 | +if(current.isEnd==true) |
| 106 | +return i |
| 107 | + j++ |
| 108 | +if(j- i< needle.length) |
| 109 | + current= current?.child?.get(haystack[j]-'a') |
| 110 | +else |
| 111 | +break |
| 112 | + } |
| 113 | + i++ |
| 114 | + } |
| 115 | + |
| 116 | +return-1 |
| 117 | + } |
| 118 | +} |
| 119 | + |
| 120 | +/* |
| 121 | +* Brute force |
| 122 | +*/ |
| 123 | +classSolution { |
| 124 | +funstrStr(haystack:String,needle:String):Int { |
| 125 | +if(needle=="")return0 |
| 126 | + |
| 127 | +for(iin0..(haystack.length- needle.length)) { |
| 128 | +for(jin0..needle.lastIndex) { |
| 129 | +if(haystack[i+ j]!= needle[j]) |
| 130 | +break |
| 131 | +if(j== needle.lastIndex) |
| 132 | +return i |
| 133 | + } |
| 134 | + } |
| 135 | + |
| 136 | +return-1 |
| 137 | + } |
| 138 | +} |