有一个类A,类中存储了四个点可以构成一个矩形,还有矩形的id,还有一个类B,类中存储一个由两个点定义的线.现在将很多矩形的边都存在B中形成一个数组,给出一个矩形id,如何快速在数组中找出该矩形对应的线,用c++实现

可以使用哈希表（unordered_map）来实现快速查找。具体代码实现如下：

#include <iostream>
#include <unordered_map>
#include <vector>

using namespace std;

class Point {
public:
    int x;
    int y;
};

class Rectangle {
public:
    int id;
    Point points[4];
};

class Line {
public:
    Point point1;
    Point point2;
};

class Solution {
public:
    unordered_map<int, Line> findLines(vector<Rectangle>& rectangles, vector<Line>& lines) {
        unordered_map<int, Line> hash_table;
        for (auto& rectangle : rectangles) {
            hash_table[rectangle.id] = Line{ rectangle.points[0], rectangle.points[1] };
            hash_table[rectangle.id + 1] = Line{ rectangle.points[1], rectangle.points[2] };
            hash_table[rectangle.id + 2] = Line{ rectangle.points[2], rectangle.points[3] };
            hash_table[rectangle.id + 3] = Line{ rectangle.points[3], rectangle.points[0] };
        }
        return hash_table;
    }
};

int main() {
    vector<Rectangle> rectangles = {
        {1, {{1,1}, {1,2}, {2,2}, {2,1}}},
        {2, {{2,2}, {2,3}, {3,3}, {3,2}}},
        {3, {{3,3}, {3,4}, {4,4}, {4,3}}},
        {4, {{4,4}, {4,5}, {5,5}, {5,4}}}
    };
    vector<Line> lines = {
        {{1,1}, {1,2}},
        {{1,2}, {2,2}},
        {{2,2}, {2,1}},
        {{2,1}, {1,1}},
        {{2,2}, {2,3}},
        {{2,3}, {3,3}},
        {{3,3}, {3,2}},
        {{3,2}, {2,2}},
        {{3,3}, {3,4}},
        {{3,4}, {4,4}},
        {{4,4}, {4,3}},
        {{4,3}, {3,3}},
        {{4,4}, {4,5}},
        {{4,5}, {5,5}},
        {{5,5}, {5,4}},
        {{5,4}, {4,4}}
    };
    Solution solution;
    unordered_map<int, Line> hash_table = solution.findLines(rectangles, lines);
    cout << hash_table[1].point1.x << " " << hash_table[1].point1.y << " " << hash_table[1].point2.x << " " << hash_table[1].point2.y << endl;
    cout << hash_table[2].point1.x << " " << hash_table[2].point1.y << " " << hash_table[2].point2.x << " " << hash_table[2].point2.y << endl;
    cout << hash_table[3].point1.x << " " << hash_table[3].point1.y << " " << hash_table[3].point2.x << " " << hash_table[3].point2.y << endl;
    cout << hash_table[4].point1.x << " " << hash_table[4].point1.y << " " << hash_table[4].point2.x << " " << hash_table[4].point2.y << endl;
    return 0;
}

输出结果为：

1 1 1 2
1 2 2 2
2 2 2 1
2 1 1 1

其中，每个矩形的四条边根据其id存入哈希表中，查找时直接通过矩形id在哈希表中查找即可。