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| 1 | +/** |
| 2 | + * @see {@link https://leetcode.com/problems/is-subsequence/?envType=study-plan&id=level-1 392. Is Subsequence} |
| 3 | + */ |
| 4 | + |
| 5 | +/** |
| 6 | + * EXPLAIN |
| 7 | + * A subsequence is defined as where letters is s occur in t in the order that they appear in s |
| 8 | + * so s = "abc", t = "ahbgdc" === true, because a appears before b appears before c appears |
| 9 | + * |
| 10 | + * all lowercase |
| 11 | + * CASE?: s = "abc", t = "abac" === true! b/c you can delete second "a" |
| 12 | + */ |
| 13 | + |
| 14 | +/** |
| 15 | + * APPROACH |
| 16 | + * |
| 17 | + * create placeholder string to collect matches |
| 18 | + * one pointer at start of s |
| 19 | + * one pointer at start of t |
| 20 | + * |
| 21 | + * LOOP through t |
| 22 | + * grab curr char |
| 23 | + * IF curr char matches pointer char of s |
| 24 | + * YES add curr char to placeholder string |
| 25 | + * advance s pointer |
| 26 | + * advance t pointer |
| 27 | + * NO ONLY advance t pointer |
| 28 | + * END LOOP |
| 29 | + * |
| 30 | + * IF placeholder length === length of s |
| 31 | + * YES return true |
| 32 | + * NO return false |
| 33 | + */ |
| 34 | + |
| 35 | +/** |
| 36 | + * ORIGINAL CODE: ACCEPTED |
| 37 | + * SPEED: 71ms - 59% |
| 38 | + * MEMORY: 42MB - 59% |
| 39 | + */ |
| 40 | +/** |
| 41 | + * @param {string} s |
| 42 | + * @param {string} t |
| 43 | + * @return {boolean} |
| 44 | + */ |
| 45 | +var isSubsequence = function (s, t) { |
| 46 | + // Track order of matching subsequence |
| 47 | + let match = ""; |
| 48 | + |
| 49 | + // Starting index of s |
| 50 | + let sPoint = 0; |
| 51 | + |
| 52 | + // Loop through t |
| 53 | + for (let tPoint = 0; tPoint < t.length; tPoint++) { |
| 54 | + // Grab both chars; s at its index, t at curr loop index |
| 55 | + const tChar = t[tPoint]; |
| 56 | + const sChar = s[sPoint]; |
| 57 | + |
| 58 | + // If both chars match, add char to match string |
| 59 | + if (tChar === sChar) { |
| 60 | + match += tChar; |
| 61 | + sPoint++; |
| 62 | + } |
| 63 | + // not equal; do nothing, just advance to next char in t |
| 64 | + } |
| 65 | + |
| 66 | + // Compare lengths |
| 67 | + // if equal: s is a subsequence of t |
| 68 | + // if not equal: s is NOT a subsequence of t |
| 69 | + if (match.length === s.length) { |
| 70 | + return true; |
| 71 | + } |
| 72 | + |
| 73 | + return false; |
| 74 | +}; |
| 75 | + |
| 76 | +/** |
| 77 | + * 2ND CODE - no match string; only integers |
| 78 | + * SPEED: 78ms - 43% |
| 79 | + * MEMORY: 41MB - 99% |
| 80 | + */ |
| 81 | +/** |
| 82 | + * @param {string} s |
| 83 | + * @param {string} t |
| 84 | + * @return {boolean} |
| 85 | + */ |
| 86 | +var isSubsequence = function (s, t) { |
| 87 | + // Starting index of s |
| 88 | + let sPoint = 0; |
| 89 | + |
| 90 | + // Loop through t |
| 91 | + for (let tPoint = 0; tPoint < t.length; tPoint++) { |
| 92 | + // Grab both chars; s at its index, t at curr loop index |
| 93 | + const tChar = t[tPoint]; |
| 94 | + const sChar = s[sPoint]; |
| 95 | + |
| 96 | + // If both chars match, increment s pointer |
| 97 | + if (tChar === sChar) { |
| 98 | + sPoint++; |
| 99 | + } |
| 100 | + // not equal; do nothing, just advance to next char in t |
| 101 | + } |
| 102 | + |
| 103 | + // Compare pointer count to s length |
| 104 | + // if equal: s is a subsequence of t |
| 105 | + // if not equal: s is NOT a subsequence of t |
| 106 | + if (sPoint === s.length) { |
| 107 | + return true; |
| 108 | + } |
| 109 | + |
| 110 | + return false; |
| 111 | +}; |
| 112 | + |
| 113 | +/** |
| 114 | + * 3RD CODE: add base cases |
| 115 | + * SPEED: 54ms - 98% |
| 116 | + * MEMORY: 41.9MB - 59% |
| 117 | + */ |
| 118 | +/** |
| 119 | + * @param {string} s |
| 120 | + * @param {string} t |
| 121 | + * @return {boolean} |
| 122 | + */ |
| 123 | +var isSubsequence = function (s, t) { |
| 124 | + // BASE CASES |
| 125 | + // s cannot be longer than t |
| 126 | + if (s.length > t.length) return false; |
| 127 | + |
| 128 | + // s and t are same length, but not same strings |
| 129 | + if (s.length === t.length && s !== t) return false; |
| 130 | + |
| 131 | + // Starting index of s |
| 132 | + let sPoint = 0; |
| 133 | + |
| 134 | + // Loop through t |
| 135 | + for (let tPoint = 0; tPoint < t.length; tPoint++) { |
| 136 | + // Grab both chars; s at its index, t at curr loop index |
| 137 | + const tChar = t[tPoint]; |
| 138 | + const sChar = s[sPoint]; |
| 139 | + |
| 140 | + // If both chars match, increment s pointer |
| 141 | + if (tChar === sChar) { |
| 142 | + sPoint++; |
| 143 | + } |
| 144 | + // not equal; do nothing, just advance to next char in t |
| 145 | + } |
| 146 | + |
| 147 | + // Compare pointer count to s length |
| 148 | + // if equal: s is a subsequence of t |
| 149 | + // if not equal: s is NOT a subsequence of t |
| 150 | + if (sPoint === s.length) { |
| 151 | + return true; |
| 152 | + } |
| 153 | + |
| 154 | + return false; |
| 155 | +}; |
| 156 | + |
| 157 | +/** |
| 158 | + * READ 02:10 |
| 159 | + * EXPLAIN 04:52 07:02 |
| 160 | + * APPROACH 13:44 20:47 |
| 161 | + * CODE 04:45 25:33 |
| 162 | + * TEST 00:17 25:51 |
| 163 | + * OPTIMIZE 14:40 40:32 |
| 164 | + */ |
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