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addBinary.java
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addBinary.java
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/**
* Created by codingBoy on 17/2/7.
*/
public class addBinary
{
/**
* Given two binary strings, return their sum (also a binary string).
For example,
a = "11"
b = "1"
Return "100".
* @param args
*
* 即二进制的加法
*/
public static void main(String[] args)
{
System.out.println(addBinary("11011","101"));
}
/**
* carry用于纪录超过该位数字超过2的,向前进1
*
* @param a
* @param b
* @return
*/
public static String addBinary(String a, String b) {
StringBuilder sb = new StringBuilder();
int i = a.length() - 1, j = b.length() -1, carry = 0;
while (i >= 0 || j >= 0) {
int sum = carry;//将进的1赋给sum
//这里需要注意的是,字符'1'的ASCAI=49,'0'=48,当然我不清楚这里后面为啥要减去一个'0',因为直接输入'1'的话输出的是0而不是49.
if (j >= 0) sum += b.charAt(j--) - '0';
if (i >= 0) sum += a.charAt(i--) - '0';
sb.append(sum % 2);//将两个二进制从右向左进行求和,并将每次结果纪录在sb中,所以最后肯定要将sb逆转。
carry = sum / 2;
}
if (carry != 0) sb.append(carry);
return sb.reverse().toString();
}
}