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Copy path两个大整数相加-优化.html
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两个大整数相加-优化.html
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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<title>Document</title>
</head>
<body></body>
<script>
function add(a, b) {
var length = a.length > b.length ? a.length + 1 : b.length + 1;
var arrA = [];
var arrB = [];
var arrR = [];
for (var i = 0; i < length; i++) {
arrA[i] = a[a.length - 1 - i] == undefined ? 0 : a[a.length - 1 - i];
arrB[i] = b[b.length - 1 - i] == undefined ? 0 : b[b.length - 1 - i];
arrR[i] = 0;
}
console.log(arrA);
for (var i = 0; i < length; i++) {
var sum = Number(arrA[i]) + Number(arrB[i]) + arrR[i];
if (sum > 9) {
arrR[i] = sum - 10;
arrR[i + 1] = 1;
} else {
arrR[i] = sum;
}
}
console.log(arrR);
if (arrR[arrR.length - 1] === 0) {
arrR.pop(arrR[arrR.length - 1]);
}
return arrR.reverse().join("");
}
console.log(add("426709752318", "95481253129"));
function addBigNumber(a, b, num) {
// 多少位为一组划分后进行相加操作
// 默认是最大安全数字长度减1
var num = num || Number.MAX_SAFE_INTEGER - 1;
// 根据num计算进位临界值（例如：999）
var num2 = num;
var range = "";
while (num2 > 0) {
range += "9";
num2--;
}
var rangeNum = Number(range);
// 根据较长字符串计算出数组长度
var length = Math.ceil(
(a.length > b.length ? a.length + 1 : b.length + 1) / num
);
var arrA = [];
var arrB = [];
var arrR = [];
for (var i = 0; i < length; i++) {
// slice方法传入负数，实现从后往前以num为跨度划分
if (i === 0) {
arrA[i] = a.slice(-num * (i + 1)) == "" ? 0 : a.slice(-num * (i + 1));
arrB[i] = b.slice(-num * (i + 1)) == "" ? 0 : b.slice(-num * (i + 1));
arrR[i] = 0;
continue;
}
arrA[i] =
a.slice(-num * (i + 1), -num * i) == ""
? 0
: a.slice(-num * (i + 1), -num * i);
arrB[i] =
b.slice(-num * (i + 1), -num * i) == ""
? 0
: b.slice(-num * (i + 1), -num * i);
arrR[i] = 0;
}
console.log(arrA);
console.log(arrB);
// 每个小单元相加
for (var i = 0; i < length; i++) {
var sum = Number(arrA[i]) + Number(arrB[i]) + arrR[i];
// 处理进位
if (sum > rangeNum) {
arrR[i] = sum - (rangeNum + 1);
arrR[i + 1] = 1;
// 与进位临界值相减后的数值需要在前面加0
// 例如arrR[i]此时为5，需要加0变成'005'
if (String(arrR[i]).length < num) {
let num3 = num - String(arrR[i]).length;
let add0 = "";
while (num3 > 0) {
add0 += "0";
num3--;
}
arrR[i] = add0 + arrR[i];
}
} else {
arrR[i] = sum;
}
}
console.log(arrR);
if (arrR[arrR.length - 1] === 0) {
arrR.pop(arrR[arrR.length - 1]);
}
return arrR.reverse().join("");
}
// 测试用，以3位数为一组
console.log(addBigNumber("426709752318", "95481253129", 3));
console.log(addBigNumber("999999999999", "99999999999", 3));
</script>
</html>