知识点指南

Arrays

Array problems are about positions and values in a sequence. The main decision is what to remember while scanning: a count, best value, previous value, current streak, or another compact state.

什么时候使用

读题时可以留意这些信号。

The input is a sequence of numbers, labels, positions, or scores.
The answer depends on neighbours, ranges, counts, or positions.
A single pass or a sorted pass can keep enough information.

常见错误

提交前可以检查这些小陷阱。

Mixing one-based and zero-based positions.
Reading outside the array bounds.
Initialising best or answer to a value that fails on negative inputs.

怎么写成代码

把知识点翻译成变量、循环、判断和更新。

Read values into a vector/list when you need positions, neighbours, sorting, or multiple passes.
Use a loop index when the position matters.
Use a direct value loop when only the value matters.
Store previous, current, best, count, or total depending on the story.

在 Block 题里长什么样

答题时通常会看到这些步骤被拆成代码块。

1Read N.
2Read the array.
3Initialise state from 0, first value, or a large/small sentinel.
4Loop over positions or values.
5Compare/update state.
6Print result.

题目里怎么出现

读题时先找这些信号，再决定答案区应该选哪些 blocks。

The statement mentions first, last, neighbouring, consecutive, position, or list.
The input gives N followed by N values.
The answer can be discovered by scanning all records once.

Track a best value

一个小型模板，展示代码和 blocks 的对应关系。

C++

int best = values[0];
for (int i = 1; i < N; i++) {
    if (values[i] > best) {
        best = values[i];
    }
}
cout << best << '\n';

Python

best = values[0]
for i in range(1, N):
    if values[i] > best:
        best = values[i]
print(best)

对应 block 顺序

1Read N and the array.
2Set best from the first value.
3Loop from the second position onward.
4Compare current value with best.
5Update best when needed.
6Output best.