Created
December 22, 2019 16:29
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function hashStringToInt(s, tableSize) { | |
let hash = 17; | |
for (let i = 0; i < s.length; i++) { | |
hash = (13 * hash * s.charCodeAt(i)) % tableSize; | |
} | |
return hash; | |
} | |
class HashTable { | |
table = new Array(3333); | |
numItems = 0; | |
resize = () => { | |
const newTable = new Array(this.table.length * 2); | |
this.table.forEach(item => { | |
if (item) { | |
item.forEach(([key, value]) => { | |
const idx = hashStringToInt(key, newTable.length); | |
if (newTable[idx]) { | |
newTable[idx].push([key, value]); | |
} else { | |
newTable[idx] = [[key, value]]; | |
} | |
}); | |
} | |
}); | |
this.table = newTable; | |
}; | |
setItem = (key, value) => { | |
this.numItems++; | |
const loadFactor = this.numItems / this.table.length; | |
if (loadFactor > 0.8) { | |
// resize | |
this.resize(); | |
} | |
const idx = hashStringToInt(key, this.table.length); | |
if (this.table[idx]) { | |
this.table[idx].push([key, value]); | |
} else { | |
this.table[idx] = [[key, value]]; | |
} | |
}; | |
getItem = key => { | |
const idx = hashStringToInt(key, this.table.length); | |
if (!this.table[idx]) { | |
return null; | |
} | |
// O(n) | |
return this.table[idx].find(x => x[0] === key)[1]; | |
}; | |
} | |
const myTable = new HashTable(); | |
myTable.setItem("firstName", "bob"); | |
myTable.setItem("lastName", "tim"); | |
myTable.setItem("age", 5); | |
myTable.setItem("dob", "1/2/3"); | |
console.log(myTable.getItem("firstName")); | |
console.log(myTable.getItem("lastName")); | |
console.log(myTable.getItem("age")); | |
console.log(myTable.getItem("dob")); |
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