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"
分析:
二进制求和,可以新定义一个string,用一个int型carry表示进位。从字符串末尾开始相加,若carry为2,则向新字符串里开头位置添0,carry置1;若carry小于2,则向新字符串里开头位置添carry的值。遍历完a、b较长的字符串并且carry等于0为止。此外要注意字符串与int型之间的转换。
class Solution {
public:
string addBinary(string a, string b) {
int len1 = a.size();
int len2 = b.size();
int carry = 0;//初始进位为0
string c = "";
int i = len1-1;
int j = len2-1;
if(len1 == 0)
return b;
if(len2 == 0)
return a;
while(i >= 0 || j >= 0 || carry > 0)
{
if(i >= 0)
{
carry += a[i] - '0';
i--;
}
if(j >= 0)
{
carry += b[j] - '0';
j--;
}
c.insert(c.begin(),carry % 2 + '0');//在c的开始位置插入低位求和的结果
carry /= 2;//若和为2,则进位为1
}
return c;
}
};