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October 27, 2021 23:30
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Calculate Fibbonacci numbers using Map() as memory cache
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const fibTest = [ | |
{ | |
in: 0, | |
out: 0, | |
}, | |
{ | |
in: 1, | |
out: 1 | |
}, | |
{ | |
in: 2, | |
out: 1 | |
}, | |
{ | |
in: 3, | |
out: 2, | |
}, | |
{ | |
in: 4, | |
out: 3, | |
}, | |
{ | |
in: 5, | |
out: 5, | |
}, | |
{ | |
in: 6, | |
out: 8, | |
}, | |
{ | |
in: 7, | |
out: 13, | |
}, | |
{ | |
in: 8, | |
out: 21, | |
}, | |
{ | |
in: 9, | |
out: 34, | |
}, | |
{ | |
in: 10, | |
out: 55, | |
}, | |
{ | |
in: 11, | |
out: 89, | |
}, | |
] | |
const memorize = (fn) => { | |
const map1 = new Map(); | |
return n => { | |
const have = map1.get(n) | |
if (have === undefined) { | |
const newVal = fn(n) | |
map1.set(n, newVal) | |
return newVal | |
} | |
return have | |
} | |
} | |
const fib = (n) => { | |
if (n === 0) return 0 | |
if (n === 1) return 1 | |
return fibMem(n-1) + fibMem(n-2) | |
} | |
const fibMem = memorize(fib) | |
fibTest.forEach(f => { | |
const out = fibMem(f.in) | |
console.log(`expect ${f.out}, actual ${out}:`, f.out === out) | |
}) | |
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