/
multiply.ts
87 lines (78 loc) · 2.08 KB
/
multiply.ts
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
import { stripTrailingZero } from "./stripTrailingZero"
export function multiply(number1, number2) {
number1 = number1.toString();
number2 = number2.toString();
/*Filter numbers*/
let negative = 0;
if (number1[0] == '-') {
negative++;
number1 = number1.substr(1);
}
if (number2[0] == '-') {
negative++;
number2 = number2.substr(1);
}
number1 = stripTrailingZero(number1);
number2 = stripTrailingZero(number2);
let decimalLength1 = 0;
let decimalLength2 = 0;
if (number1.indexOf('.') != -1) {
decimalLength1 = number1.length - number1.indexOf('.') - 1;
}
if (number2.indexOf('.') != -1) {
decimalLength2 = number2.length - number2.indexOf('.') - 1;
}
let decimalLength = decimalLength1 + decimalLength2;
number1 = stripTrailingZero(number1.replace('.', ''));
number2 = stripTrailingZero(number2.replace('.', ''));
if (number1.length < number2.length) {
let temp = number1;
number1 = number2;
number2 = temp;
}
if (number2 == '0') {
return '0';
}
/*
* Core multiplication
*/
let length = number2.length;
let carry = 0;
let positionVector = [];
let currentPosition = length - 1;
let result = "";
for (let i = 0; i < length; i++) {
positionVector[i] = number1.length - 1;
}
for (let i = 0; i < 2 * number1.length; i++) {
let sum = 0;
for (let j = number2.length - 1; j >= currentPosition && j >= 0; j--) {
if (positionVector[j] > -1 && positionVector[j] < number1.length) {
sum += parseInt(number1[positionVector[j]--]) * parseInt(number2[j]);
}
}
sum += carry;
carry = Math.floor(sum / 10);
result = sum % 10 + result;
currentPosition--;
}
/*
* Formatting result
*/
result = stripTrailingZero(adjustDecimal(result, decimalLength));
if (negative == 1) {
result = '-' + result;
}
return result;
}
/*
* Add decimal point
*/
function adjustDecimal(number, decimal) {
if (decimal == 0)
return number;
else {
number = (decimal >= number.length) ? ((new Array(decimal - number.length + 1)).join('0') + number) : number;
return number.substr(0, number.length - decimal) + '.' + number.substr(number.length - decimal, decimal)
}
}