0067. Add Binary (E)

Add Binary (E)

題目

Given two binary strings, return their sum (also a binary string).

The input strings are both non-empty and contains only characters 1 or 0.

Example 1:

Input: a = "11", b = "1"
Output: "100"

Example 2:

Input: a = "1010", b = "1011"
Output: "10101"

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題意

實現以字符串表示的二進制加法。

思路

直接從後往前按位相加便可。

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代碼實現

Java

class Solution {
    public String addBinary(String a, String b) {
        int i = a.length() - 1, j = b.length() - 1;
        int carry = 0;
        StringBuilder bits = new StringBuilder();
        
        while (i >= 0 || j >= 0 || carry == 1) {
            int sum = carry;
            if (i >= 0) {
                sum += a.charAt(i--) - '0';
            }
            if (j >= 0) {
                sum += b.charAt(j--) - '0';
            }
            bits.append(sum % 2);
            carry = sum / 2;
        }

        return bits.reverse().toString();
    }
}

JavaScript

/**
 * @param {string} a
 * @param {string} b
 * @return {string}
 */
var addBinary = function (a, b) {
  let i = 0
  let carry = 0
  let ans = []
  while (i < a.length || i < b.length) {
    let sum = carry
    sum += i < a.length ? +a[a.length - 1 - i] : 0
    sum += i < b.length ? +b[b.length - 1 - i] : 0
    carry = Math.trunc(sum / 2)
    sum %= 2
    ans.unshift(sum)
    i++
  }
  if (carry) {
    ans.unshift(carry)
  }
  return ans.join('')
}