|
| 1 | +/** |
| 2 | + * @see {@link https://leetcode.com/problems/isomorphic-strings/?envType=study-plan&id=level-1 205. Isomorphic Strings} |
| 3 | + */ |
| 4 | + |
| 5 | +/** |
| 6 | + * EXPLAIN |
| 7 | + * Isomorphic means ONLY key to one value |
| 8 | + * In this case, one letter can be mapped to only one letter (self-map ok) |
| 9 | + * |
| 10 | + * s = "egg", t = "add" |
| 11 | + * > IS isomorphic: e -> a, g -> d |
| 12 | + * |
| 13 | + * s = "foo", t = "bar" |
| 14 | + * > IS NOT isomorphic, two unique letters in s, three in t, not uniquely paired |
| 15 | + * |
| 16 | + * EXTRA EXAMPLE: |
| 17 | + * |
| 18 | + * s = "baby", t = "fool" |
| 19 | + * > IS NOT isomorphic, three unique letters in both, BUT order NOT preserved |
| 20 | + */ |
| 21 | + |
| 22 | +/** |
| 23 | + * APPROACH |
| 24 | + * |
| 25 | + * create blank map |
| 26 | + * |
| 27 | + * both same string length ? return false |
| 28 | + * |
| 29 | + * LOOP through both words same time |
| 30 | + * check to see if map has string 1 letter mapped |
| 31 | + * NO: set string 1 letter to string 2 letter |
| 32 | + * YES: does string 1 letter key have string 2 letter value |
| 33 | + * NO: return false |
| 34 | + * END LOOP |
| 35 | + * |
| 36 | + * made it out of loop; return true |
| 37 | + */ |
| 38 | + |
| 39 | +/** |
| 40 | + * ORIGINAL CODE |
| 41 | + * SPEED: 67ms - 97% |
| 42 | + * MEMORY: 46.2MB - 22% |
| 43 | + */ |
| 44 | +/** |
| 45 | + * @param {string} s |
| 46 | + * @param {string} t |
| 47 | + * @return {boolean} |
| 48 | + */ |
| 49 | +var isIsomorphic = function (s, t) { |
| 50 | + // Both strings need the same number of unique letters for this to work. |
| 51 | + const firstLetters = new Set(s); |
| 52 | + const secondLetters = new Set(t); |
| 53 | + if (firstLetters.size !== secondLetters.size) { |
| 54 | + return false; |
| 55 | + } |
| 56 | + |
| 57 | + const letterMap = new Map(); |
| 58 | + |
| 59 | + for (let i = 0; i < s.length; i++) { |
| 60 | + const key = s[i]; |
| 61 | + const val = t[i]; |
| 62 | + |
| 63 | + if (!letterMap.has(key)) { |
| 64 | + letterMap.set(key, val); |
| 65 | + } else if (letterMap.get(key) !== val) { |
| 66 | + return false; |
| 67 | + } |
| 68 | + } |
| 69 | + return true; |
| 70 | +}; |
| 71 | + |
| 72 | +/** |
| 73 | + * Same code, but using an object instead of a Map |
| 74 | + * SPEED: 78ms - 80% |
| 75 | + * MEMORY: 46MB - 23% |
| 76 | + */ |
| 77 | +/** |
| 78 | + * @param {string} s |
| 79 | + * @param {string} t |
| 80 | + * @return {boolean} |
| 81 | + */ |
| 82 | +var isIsomorphic = function (s, t) { |
| 83 | + // Both strings need the same number of unique letters for this to work. |
| 84 | + const firstUniques = new Set(s); |
| 85 | + const secondUniques = new Set(t); |
| 86 | + if (firstUniques.size !== secondUniques.size) { |
| 87 | + return false; |
| 88 | + } |
| 89 | + |
| 90 | + // Can be a regular object b/c insertion order doesn't matter. |
| 91 | + const letterMap = {}; |
| 92 | + |
| 93 | + // Loop through both strings at same time |
| 94 | + for (let i = 0; i < s.length; i++) { |
| 95 | + const key = s[i]; |
| 96 | + const val = t[i]; |
| 97 | + |
| 98 | + // IF key does not exist |
| 99 | + // set key to val |
| 100 | + // ELSE IF existing val for key does not equal current val |
| 101 | + // return false |
| 102 | + if (!letterMap.hasOwnProperty(key)) { |
| 103 | + letterMap[key] = val; |
| 104 | + } else if (letterMap[key] !== val) { |
| 105 | + return false; |
| 106 | + } |
| 107 | + } |
| 108 | + // made it out of the loop without triggering a false |
| 109 | + // strings ARE isomorphic |
| 110 | + return true; |
| 111 | +}; |
| 112 | + |
| 113 | +/** |
| 114 | + * COMPLEXITY |
| 115 | + * TIME: O(N); to loop through the strings once for Set creation, then key checking |
| 116 | + * SPACE: O(N): size of Sets and key-value pairs of map object is dependent on string length |
| 117 | + */ |
| 118 | + |
| 119 | +/** |
| 120 | + * READ 01:24 |
| 121 | + * EXPLAIN 02:29 03:53 |
| 122 | + * APPROACH 08:09 12:03 |
| 123 | + * CODE 04:39 16:52 |
| 124 | + * TEST 11:08 28:00 |
| 125 | + * OPTIMIZE 08:51 36:51 |
| 126 | + */ |
0 commit comments