public class P0067AddBinary {

//这道题目与415题 add strings类似，一个是针对二进制，一个是针对十进制 /，%

public String addBinary0(String a, String b){

String res = "";

int index_a = a.length()-1;

int index_b = b.length()-1;

int carry = 0;//进位初始值

while(index_a>=0 || index_b>=0){

int aNum = index_a>=0? a.charAt(index_a)-'0':0;

//如果index没有out of boundary,则取对应位置上的字符，然后转成int类型，否则取0

int bNum = index_b>=0?b.charAt(index_b)-'0':0;

int tempSum = aNum + bNum + carry;

carry = tempSum/2;

int remain = tempSum % 2;

res = String.valueOf(remain)+res;

index_a--;

index_b--;

}

if(carry ==1) res = String.valueOf(carry)+res;

return res;

}

public String addBinary(String a, String b){//StringBuilder的效率会更高

StringBuilder sb = new StringBuilder();

int i = a.length()-1;

int j = b.length()-1;

int carry = 0;

while(i>=0 || j>=0){

int numA = i>=0?a.charAt(i)-'0':0;

int numB = j>=0?b.charAt(j)-'0':0;

int sum = numA + numB + carry;

carry = sum /2;

int remain = sum % 2;

sb.append(remain);

i--;

j--;

}

if(carry ==1) sb.append(carry);

return sb.reverse().toString();

}

}

/*

P0067AddBinary p67 = new P0067AddBinary();

System.out.println(p67.addBinary("11", "1"));

System.out.println(p67.addBinary("1010", "1011"));

*/