js 版本
function compare(p, q) {
while (p[0] === '0') {
p = p.substr(1);
}
while (q[0] === '0') {
q = q.substr(1);
}
if (p.length > q.length) {
return 1;
} else if (p.length < q.length) {
return -1;
} else {
let i = 0;
let a, b;
while (1) {
a = parseInt(p.charAt(i));
b = parseInt(q.charAt(i));
if (a > b) {
return 1;
} else if (a < b) {
return -1;
} else if (i === p.length - 1) {
return 0;
}
i++;
}
}
}
function divide(A, B) {
let result = [];
let max = 9;
let point = 5;
let fill = 0;
if (B.length - A.length > 0) {
point += fill = B.length - A.length;
}
for (let i = 0; i < point; i++) {
A += '0';
}
let la = A.length;
let lb = B.length;
let b0 = parseInt(B.charAt(0));
let Adb = A.substr(0, lb);
A = A.substr(lb);
let temp, r;
for (let j = 0; j < la - lb + 1; j++) {
while (Adb[0] === '0') {
Adb = Adb.substr(1);
}
if (Adb.length === lb) {
max = Math.ceil((parseInt(Adb.charAt(0)) + 1) / b0); // 不可能取到这个最大值,1<= max <= 10
} else if (Adb.length > lb) {
max = Math.ceil((parseInt(Adb.substr(0, 2)) + 1) / b0);
} else {
result.push(0);
Adb += A[0];
A = A.substr(1);
continue;
}
for (let i = max - 1; i >= 0; i--) {
if (i === 0) {
result.push(0);
Adb += A[0];
A = A.substr(1);
break;
} else {
temp = temp || multiply(B, i + '');
r = compare(temp, Adb);
if (r === 0 || r === -1) {
result.push(i);
if (r) {
Adb = reduce(Adb, temp);
Adb += A[0];
} else {
Adb = A[0];
}
A = A.substr(1);
break;
} else {
temp = reduce(temp, B);
}
}
}
temp = 0;
}
for (let i = 0; i < fill; i++) {
result.unshift('0');
}
result.splice(result.length - point, 0, '.');
if (!result[0] && result[1] !== '.') {
result.shift();
}
point = false;
let position = result.indexOf('.');
for (let i = position + 1; i < result.length; i++) {
if (result[i]) {
point = true;
break;
}
}
if (!point) {
result.splice(position);
}
result = result.join('');
return result;
}
function multiply(A, B) {
let result = [];
(A += ''), (B += '');
const l = -4; // 以支持百万位精确运算,但速度减半
let r1 = [],
r2 = [];
while (A !== '') {
r1.unshift(parseInt(A.substr(l)));
A = A.slice(0, l);
}
while (B !== '') {
r2.unshift(parseInt(B.substr(l)));
B = B.slice(0, l);
}
let index, value;
for (let i = 0; i < r1.length; i++) {
for (let j = 0; j < r2.length; j++) {
value = 0;
if (r1[i] && r2[j]) {
value = r1[i] * r2[j];
}
index = i + j;
if (result[index]) {
result[index] += value;
} else {
result[index] = value;
}
}
}
for (let i = result.length - 1; i > 0; i--) {
result[i] += '';
if (result[i].length > -l) {
result[i - 1] += parseInt(result[i].slice(0, l));
result[i] = result[i].substr(l);
}
while (result[i].length < -l) {
result[i] = '0' + result[i];
}
}
if (result[0]) {
result = result.join('');
} else {
result = '0';
}
return result;
}
function add(A, B) {
let result = [];
(A += ''), (B += '');
const l = -15;
while (A !== '' && B !== '') {
result.unshift(parseInt(A.substr(l)) + parseInt(B.substr(l)));
A = A.slice(0, l);
B = B.slice(0, l);
}
A += B;
for (let i = result.length - 1; i > 0; i--) {
result[i] += '';
if (result[i].length > -l) {
result[i - 1] += 1;
result[i] = result[i].substr(1);
} else {
while (result[i].length < -l) {
result[i] = '0' + result[i];
}
}
}
while (A && (result[0] + '').length > -l) {
result[0] = (result[0] + '').substr(1);
result.unshift(parseInt(A.substr(l)) + 1);
A = A.slice(0, l);
}
if (A) {
while ((result[0] + '').length < -l) {
result[0] = '0' + result[0];
}
result.unshift(A);
}
if (result[0]) {
result = result.join('');
} else {
result = '0';
}
return result;
}
function reduce(A, B) {
let result = [];
(A += ''), (B += '');
while (A[0] === '0') {
A = A.substr(1);
}
while (B[0] === '0') {
B = B.substr(1);
}
const l = -15;
let N = '1';
for (let i = 0; i < -l; i++) {
N += '0';
}
N = parseInt(N);
while (A !== '' && B !== '') {
result.unshift(parseInt(A.substr(l)) - parseInt(B.substr(l)));
A = A.slice(0, l);
B = B.slice(0, l);
}
if (A !== '' || B !== '') {
let s = B === '' ? 1 : -1;
A += B;
while (A !== '') {
result.unshift(s * parseInt(A.substr(l)));
A = A.slice(0, l);
}
}
while (result.length !== 0 && result[0] === 0) {
result.shift();
}
let s = '';
if (result.length === 0) {
result = 0;
} else if (result[0] < 0) {
s = '-';
for (let i = result.length - 1; i > 0; i--) {
if (result[i] > 0) {
result[i] -= N;
result[i - 1]++;
}
result[i] *= -1;
result[i] += '';
while (result[i].length < -l) {
result[i] = '0' + result[i];
}
}
result[0] *= -1;
} else {
for (let i = result.length - 1; i > 0; i--) {
if (result[i] < 0) {
result[i] += N;
result[i - 1]--;
}
result[i] += '';
while (result[i].length < -l) {
result[i] = '0' + result[i];
}
}
}
if (result) {
while ((result[0] = parseInt(result[0])) === 0) {
result.shift();
}
result = s + result.join('');
}
return result;
}
php 版本
php中的bcmul()函数是一个内置函数,用于将两个任意精度的数字相乘。此函数接受两个任意精度的数字作为字符串,并在将结果缩放到指定精度后返回两个数字的乘法