Linear Search
Linear search checks elements one by one until it finds the target or reaches the end.
先从这个心智模型开始
Linear search checks elements one by one until it finds the target or reaches the end.
它如何工作，不堆砌不必要的术语
It needs no sorting or preprocessing.
Worst-case it examines every element, so time is O(n).
把算法读成一连串决策
Write the preconditions first (sorted? uniform? random access?).
Maintain a clear search interval/state.
Prove that each step makes progress toward termination.
Read a tiny input by hand and write down the state after every important operation. For Linear Search, the goal is to make the invariant visible rather than to memorize code.
function linearSearch(items, target) {
for (let i = 0; i < items.length; i++) {
if (items[i] === target) return i;
}
return -1;
}不要死记语法。跟踪每一行中发生变化的状态，并把它与上面描述的不变量联系起来。
O(n)
Do not quote this complexity mechanically. Ask which operation or input dimension it describes, then derive the cost from the loops, recursion depth, data-structure operations and any preprocessing assumptions.
适用场景
- Match the algorithm to the structure and preprocessing state of the data.
通常哪里会出错
- Violating preconditions.
- Boundary and termination bugs.
专业回答结构
Do not dismiss it as 'bad'. For small, unsorted or one-off searches it may be the simplest and correct choice.
What problem does Linear Search solve?
Linear search checks elements one by one until it finds the target or reaches the end.
关于复杂度应该提到什么？
Its typical cost here is O(n), but a complete answer should connect that cost to the representation, input constraints and the dominant operations.
最常见的错误是什么？
Violating preconditions.