1、题目描述
2、题目分析
使用string 的逆向指针，做二进制加法，注意进位问题就可以。
3、代码
1 string addBinary(string a, string b) { 2 3 string::reverse_iterator it_a = a.rbegin() ; 4 string::reverse_iterator it_b = b.rbegin() ; 5 6 string s; 7 string s0 = "0"; 8 string s1 = "1"; 9 int up = 0; 10 while( it_a != a.rend() && it_b != b.rend() ){ 11 if( *it_a - '0' + *it_b - '0' + up == 1 ){ 12 s = s1 + s; 13 up = 0; 14 }else if( *it_a - '0' + *it_b - '0' + up == 0 ){ 15 s = s0 + s; 16 up = 0; 17 }else if( *it_a - '0' + *it_b - '0' + up == 2 ){ 18 s = s0 + s; 19 up=1; 20 }else if( *it_a - '0' + *it_b - '0' + up == 3 ){ 21 s = s1 + s; 22 up = 1; 23 } 24 ++it_a ; 25 ++it_b ; 26 } 27 28 while( it_a != a.rend() ){ 29 if( *it_a - '0' + up == 0 ){ 30 s = s0 + s; 31 up = 0; 32 }else if( *it_a - '0' + up == 1){ 33 s = s1 + s; 34 up = 0; 35 }else{ 36 s = s0 + s; 37 up = 1; 38 } 39 ++it_a ; 40 } 41 42 while( it_b != b.rend() ){ 43 if( *it_b - '0' + up == 0 ){ 44 s = s0 + s; 45 up = 0; 46 }else if(*it_b - '0' + up == 1){ 47 s = s1 + s; 48 up =0; 49 }else{ 50 s = s0 + s; 51 up = 1; 52 } 53 ++it_b; 54 } 55 56 if( up == 1 ){ 57 s = s1 + s; 58 } 59 60 return s; 61 62 }