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Tower of Hanoi Backup
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| // given a number of intervals and number of backup slots, console log out each backup slots age for every interval | |
| const printBackupIntervals = (intervals, backupSlots) => { | |
| let points = {}; | |
| const pad = String(Math.pow(2, backupSlots - 1)).split("").map(c => "0").join(""); | |
| for (let i = 1; i < intervals; i++) { | |
| Object.keys(points).forEach(k => points[k]++); | |
| const k = tower(i, backupSlots).charCodeAt(0); | |
| points[k] = 1; | |
| console.log("Day " + i + ": " + Object.keys(points).map(p => { | |
| const str = String(points[p]); | |
| return String.fromCharCode(p) + ": " + pad.substring(0, pad.length - str.length) + str; | |
| }).join(", ")); | |
| } | |
| } | |
| // how many days range do we get from each slot? | |
| const backupRange = (slot) => { | |
| if (slot === 1) return [0, 1]; | |
| if (slot === 2) return [1, 2]; | |
| if (slot === 3) return [2, 3]; | |
| const base = Math.pow(2, slot - 2) - 1; | |
| const base2 = Math.pow(2, slot - 1) - 1; | |
| return [base, base2]; | |
| } | |
| /* | |
| 1: 0 - 1 days | |
| 2: 1 - 2 days | |
| 3: 2 - 3 days | |
| 4: 3 - 7 days | |
| 5: 7 - 15 days | |
| 6: 15 - 31 days | |
| 7: 31 - 63 days | |
| 8: 63 - 127 days | |
| 9: 127 - 255 days | |
| 10: 255 - 511 days | |
| 11: 511 - 1,023 days | |
| 12: 1,023 - 2,047 days | |
| 13: 2,047 - 4,095 days | |
| 14: 4,095 - 8,191 days | |
| 15: 8,191 - 16,383 days | |
| 16: 16,383 - 32,767 days | |
| 17: 32,767 - 65,535 days | |
| 18: 65,535 - 131,071 days | |
| 19: 131,071 - 262,143 days | |
| */ |
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| // given an increment from the first backup and the number of backup slots available, | |
| // provide which backup slot this backup belongs in. | |
| // returns a letter fom "A" on up to denote which backup slot to use. | |
| const tower = (backupNum, backupCount) => { | |
| const max = Math.pow(2, backupCount - 1); | |
| const backupDay = backupNum % max; | |
| if (backupDay === 1) { // begining of cycle | |
| return "A"; | |
| } else if (backupDay === 0) { // end of cycle | |
| return String.fromCharCode(64 + backupCount); | |
| } | |
| return tower(backupDay, backupCount - 1); | |
| }; | |
| /* | |
| // first backup with 5 slots: | |
| tower(1, 5) => "A" | |
| // 8th backup done with 5 slots: | |
| tower(8, 5) => "D" | |
| // 2,398th backup with 5 slots | |
| tower(2938, 5) => "B" | |
| */ |
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