add: 大数相加

Author: Eric-art-coder

src/number/大数相加.js

@@ -0,0 +1,20 @@
+// 也是小米的一面面试题
+// JS在存放整数的时候有一个安全范围的，一旦数字超过这个范围便会损失精度
+let a = "9007199254740991"
+let b = "1234567899999999999"
+
+function add(a, b) {
+  let maxLength = Math.max(a.length, b.length)
+  a = a.padStart(maxLength, '0')
+  b = b.padStart(maxLength, '0')
+  let t = 0, f = 0, sum = ""
+  for(let i = maxLength - 1; i >= 0; i--) {
+    t = parseInt(a[i]) + parseInt(b[i]) + f
+    f = Math.floor(t/10)
+    sum = t % 10 + sum
+  }
+  if(f == 1) sum = '1' + sum
+  return sum
+}
+
+console.log(add(a, b)) // 1243575099254740990