LeetCode-Add Binary

怼烎@ 2022-08-06 15:15 20阅读 0赞

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

For example,  
a = `"11"`  
b = `"1"`

Return `"100"`.

自己的解答：

public String addBinary(String a, String b) {
        	if (a == null || b == null) 
        		return null;
        	int base = 2;
        	int max = a.length() > b.length() ? a.length() : b.length();
            char[] result = new char[max+1];
            int sum, carry = 0, i, j, k;
            for (i = a.length()-1, j = b.length()-1, k = result.length-1; i >= 0 && j >= 0; i--,j--) {
            	sum = a.charAt(i) + b.charAt(j) + carry- 2*'0';
            	carry = sum/base;
            	result[k--] = (char) (sum%base + '0');
            }
            while (i >= 0) {
            	sum = a.charAt(i) + carry- '0';
            	carry = sum/base;
            	result[k--] = (char) (sum%base + '0');
            	i--;
            }
            while (j >= 0) {
            	sum = b.charAt(j) + carry- '0';
            	carry = sum/base;
            	result[k--] = (char) (sum%base + '0');
            	j--;
            }
            if (carry == 1) {
            	result[0] = '1';
            	return String.copyValueOf(result, 0, result.length);
            }
            return String.copyValueOf(result, 1, result.length-1);
        }

最通用的方法，或者说，以上代码改成八进制，十进制，十六进制都是可以用的，只需要修改base的值即可。也比较适合于大数相加。贴一下别人的代码，大同小异：

public String addBinary(String a, String b) {
            if(a == null || a.isEmpty()) {
                return b;
            }
            if(b == null || b.isEmpty()) {
                return a;
            }
            char[] aArray = a.toCharArray();
            char[] bArray = b.toCharArray();
            StringBuilder stb = new StringBuilder();
    
            int i = aArray.length - 1;
            int j = bArray.length - 1;
            int aByte;
            int bByte;
            int carry = 0;
            int result;
    
            while(i > -1 || j > -1 || carry == 1) {
                aByte = (i > -1) ? Character.getNumericValue(aArray[i--]) : 0;
                bByte = (j > -1) ? Character.getNumericValue(bArray[j--]) : 0;
                result = aByte ^ bByte ^ carry;
                carry = ((aByte + bByte + carry) >= 2) ? 1 : 0;
                stb.append(result);
            }
            return stb.reverse().toString();
        }