Add Binary

最新推荐文章于 2022-04-09 11:43:16 发布

cgdong2014

最新推荐文章于 2022-04-09 11:43:16 发布

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分类专栏： LeetCode

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

For example,
a = "11"
b = "1"
Return "100".

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思路： Using stringBuilder to reverse these two strings,then add them to the end of the short one. Add the rest of the longer one. At last, reverse the result and create a new String by this result.
易错点：1. carry 应该直接加在 cur上。 2. i 第一次只加到两个string 的较短的结尾，千万别忘记把剩余的长的也加上。 3. 最后剩余一个carry 小尾巴有可能为1.

public class Solution {
    public String addBinary(String a, String b) {
        StringBuilder sb1 = new StringBuilder(a);
        StringBuilder sb2 = new StringBuilder(b);
        sb1 = sb1.reverse();
        sb2 = sb2.reverse();
        StringBuilder ret = new StringBuilder();
        int i = 0;
        int carry = 0;
        while(i < sb1.length() && i < sb2.length()){
            int cur = sb1.charAt(i) - '0' + sb2.charAt(i) - '0' + carry;
            ret.append(cur % 2);
            carry = cur / 2;
            i++;
        }
        sb1 = (sb1.length() > sb2.length()) ? sb1 : sb2;
        while(i < sb1.length()){
            int cur = sb1.charAt(i) - '0' + carry;
            ret.append(cur % 2);
            carry = cur / 2;
            i++;
        }
        if(carry > 0){
            ret.append(1);
        }
        return new String(ret.reverse());
    }
}