用比喻和步进图讲透一道算法题

只是写法示意，不是完整程序。

// ANS 算法可视化单步执行快照记录器 (ans-algo-stepper.ts)
export function traceAnsBinarySearch(nums: number[], target: number) {
  const steps: Array<{ lo: number; hi: number; mid: number }> = [];
  let lo = 0, hi = nums.length - 1;
  while (lo <= hi) {
    const mid = (lo + hi) >> 1;
    steps.push({ lo, hi, mid });
    if (nums[mid] === target) break;
    nums[mid] < target ? (lo = mid + 1) : (hi = mid - 1);
  }
  return steps;
}