二进制炸弹实验 BinaryBombs( 五 ) _生活百科

现在从最终返回值5倒推一下：

$5 = 2 * 2 + 1$，$res = (14 - 0) / 2 + 0 = 7$当前func4(a, 0, 14, 7) 则递归func4(a, 8, 14, 7)
$2 = 2 * 1$， $res = (14 - 8) / 2 + 8 = 11$ 当前func4(a, 8, 14, 11) 则递归func4(a, 8, 10, 11)
$1 = 2 * 0 + 1$，$res = (10 - 8) / 2 + 8 = 9$当前func4(a, 8, 10, 9) 则递归func4(a, 10, 10, 9)
$0 = 0$，递归终止条件，此时$ res = (10 - 10) / 2 + 10 = 10$

好，那么可以得出 a = 10

则答案为 10, 5

汇编代码：

点击查看代码0000000000401518 <func4>: 401518: 55 push %rbp 401519: 48 89 e5 mov %rsp,%rbp 40151c: 89 d1 mov %edx,%ecx 40151e: 29 f1 sub %esi,%ecx 401520: 89 c8 mov %ecx,%eax 401522: c1 e8 1f shr $0x1f,%eax 401525: 01 c8 add %ecx,%eax 401527: d1 f8 sar %eax 401529: 01 f0 add %esi,%eax 40152b: 39 f8 cmp %edi,%eax 40152d: 7f 09 jg 401538 <func4+0x20> 40152f: 7c 13 jl 401544 <func4+0x2c> 401531: b8 00 00 00 00 mov $0x0,%eax 401536: 5d pop %rbp 401537: c3 retq 401538: 8d 50 ff lea -0x1(%rax),%edx 40153b: e8 d8 ff ff ff callq 401518 <func4> 401540: 01 c0 add %eax,%eax 401542: eb f2 jmp 401536 <func4+0x1e> 401544: 8d 70 01 lea 0x1(%rax),%esi 401547: e8 cc ff ff ff callq 401518 <func4> 40154c: 8d 44 00 01 lea 0x1(%rax,%rax,1),%eax 401550: eb e4 jmp 401536 <func4+0x1e>0000000000401552 <phase_4>: 401552: 55 push %rbp 401553: 48 89 e5 mov %rsp,%rbp 401556: 48 83 ec 10 sub $0x10,%rsp 40155a: 48 8d 4d f8 lea -0x8(%rbp),%rcx 40155e: 48 8d 55 fc lea -0x4(%rbp),%rdx 401562: be 1f 33 40 00 mov $0x40331f,%esi 401567: b8 00 00 00 00 mov $0x0,%eax 40156c: e8 9f fb ff ff callq 401110 <__isoc99_sscanf@plt> 401571: 83 f8 02 cmp $0x2,%eax 401574: 75 0c jne 401582 <phase_4+0x30> 401576: 8b 45 fc mov -0x4(%rbp),%eax 401579: 85 c0 test %eax,%eax 40157b: 78 05 js 401582 <phase_4+0x30> 40157d: 83 f8 0e cmp $0xe,%eax 401580: 7e 05 jle 401587 <phase_4+0x35> 401582: e8 b9 03 00 00 callq 401940 <explode_bomb> 401587: ba 0e 00 00 00 mov $0xe,%edx 40158c: be 00 00 00 00 mov $0x0,%esi 401591: 8b 7d fc mov -0x4(%rbp),%edi 401594: e8 7f ff ff ff callq 401518 <func4> 401599: 83 f8 05 cmp $0x5,%eax 40159c: 75 06 jne 4015a4 <phase_4+0x52> 40159e: 83 7d f8 05 cmpl $0x5,-0x8(%rbp) 4015a2: 74 05 je 4015a9 <phase_4+0x57> 4015a4: e8 97 03 00 00 callq 401940 <explode_bomb> 4015a9: c9 leaveq 4015aa: c3 retq