这是编程设计版本， 来， 程序说话
从坐标0开始交替按等比数列打枪(等待)和右移(追赶)
时刻  坐标  打枪  右移
0     0    1    2
1     2    4    8
5     10   16   32
21    42   64   128
85    170  256  512
....
每一轮的第一枪，（坐标-时刻）是0，1，5，21，85...，是递增的，总能追上右边的蚂蚁
每一轮最后一枪，（坐标-时刻）-1，-3，-11，-43，-171...，是递减的，最后总能被左边蚂蚁追上

#include<iostream>
#include<vector>
#include<cinttypes>
#include<iomanip>
using namespace std;

class Ant {
public:
  Ant(long p) {
    pos = p;
  }
  void forWard(long i = 1) {
    pos += i;
  }

  bool hit(long i) {
    return i == pos;
  }

  void print() {
    cout << setw(5) << pos;
  }
private:
  long pos;
};

int main(int argc, char** argv) {
  Ant ant(stoll(argv[1]));

  long pos = 0;
  long time = 0;
  long step = 1;

  while (step < INT64_MAX/2) {
    // shot step bullets on position pos
    cout << "time = " << setw(5) << time << ", antPost =";
    ant.print();
    cout << ", pos = " << setw(5) << pos << ", will Shoot "
         << setw(8) << step << " bullets" << endl;
    for (long i = 0; i < step; ++i) {
      if (ant.hit(pos)) {
          cout << "Bingo! pos = " << pos << ", time = " << time << endl;
          exit(0);
      }
      time++;
      ant.forWard();
    }
    step = step * 2;
    pos += step; // gun forward step
    step = step * 2;
  }
}

看看输出
File Edit Options Buffers Tools Complete In/Out Signals Help
~/code/0730 $ ./a.out 9975
time =     0, antPost = 9975, pos =     0, will Shoot        1 bullets
time =     1, antPost = 9976, pos =     2, will Shoot        4 bullets
time =     5, antPost = 9980, pos =    10, will Shoot       16 bullets
time =    21, antPost = 9996, pos =    42, will Shoot       64 bullets
time =    85, antPost =10060, pos =   170, will Shoot      256 bullets
time =   341, antPost =10316, pos =   682, will Shoot     1024 bullets
time =  1365, antPost =11340, pos =  2730, will Shoot     4096 bullets
time =  5461, antPost =15436, pos = 10922, will Shoot    16384 bullets
time = 21845, antPost =31820, pos = 43690, will Shoot    65536 bullets
Bingo pos = 43690, time = 33715
~/code/0730 $ ./a.out -45738
time =     0, antPost =-45738, pos =     0, will Shoot        1 bullets
time =     1, antPost =-45737, pos =     2, will Shoot        4 bullets
time =     5, antPost =-45733, pos =    10, will Shoot       16 bullets
time =    21, antPost =-45717, pos =    42, will Shoot       64 bullets
time =    85, antPost =-45653, pos =   170, will Shoot      256 bullets
time =   341, antPost =-45397, pos =   682, will Shoot     1024 bullets
time =  1365, antPost =-44373, pos =  2730, will Shoot     4096 bullets
time =  5461, antPost =-40277, pos = 10922, will Shoot    16384 bullets
time = 21845, antPost =-23893, pos = 43690, will Shoot    65536 bullets
time = 87381, antPost =41643, pos = 174762, will Shoot   262144 bullets
Bingo pos = 174762, time = 220500
【 在 stub 的大作中提到: 】
: 有一个无限长的整数刻度的坐标轴，有一只蚂蚁在某一个整数刻度上，但是具体位置未知，现在蚂蚁每秒钟都会向正方向前进一格。你有一把手枪，每秒钟你能向坐标轴的某个刻度开一枪，之后只能知道打中还是没打中，请你设计一种开枪的策略，保证最终一定能打中这只蚂蚁。
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