vector<int> numCount; while(cin>>inputData)什么意思

`vector<int> numCount;` 是C++语言中的一行代码，它声明了一个名为`numCount`的向量（vector），用于存储整型（int）数据。向量是一种动态数组，可以根据需要动态地增加和减少其容量。

`while(cin>>inputData)`是C++语言中的一个循环结构，它使用标准输入流（cin）从标准输入（通常是键盘输入或重定向的文件输入）读取数据。每次循环迭代时，`cin`尝试从输入中读取下一个值，并将其存储在变量`inputData`中。如果成功读取一个值，则循环继续；如果输入到达文件结束符（EOF）或发生读取错误，则循环终止。

结合来看，这两行代码通常出现在一个程序中，用于读取一系列的整数，并将它们存储在`numCount`向量中。例如，以下代码段将持续读取输入直到遇到文件结束符：

#include <iostream>
#include <vector>

using namespace std;

int main() {
    vector<int> numCount;
    int inputData;
    while(cin >> inputData) {
        numCount.push_back(inputData); // 将读取的数据添加到向量numCount中
    }
    // 程序继续执行其他操作，numCount现在包含了所有读取的整数
    return 0;
}

相关问题

Add detailed comments to the following code and give the code: #include <bits/stdc++.h> using namespace std; const int INF = 0x3f3f3f3f; const int MAXN = 25; const int MAXM = 45; struct Edge { int to, next, w; } edge[MAXM]; int main() { int head[MAXN], cnt=0; int dis[MAXN][MAXN], vis[MAXN]; int shield[MAXN][MAXN], d[MAXN][MAXN]; int n, m; memset(dis, INF, sizeof(dis)); memset(head, -1, sizeof(head)); memset(shield, 0, sizeof(shield)); cin >> n >> m; for (int i = 1; i <= m; i++) { int u, v, w; cin >> u >> v >> w; edge[cnt].to = v; edge[cnt].w = w; edge[cnt].next = head[u]; head[u] = cnt++; dis[u][v] = min(dis[u][v], w); } for (int k = 1; k <= n; k++) { for (int i = 1; i <= n; i++) { for (int j = 1; j <= n; j++) { if (i == j) continue; dis[i][j] = min(dis[i][j], dis[i][k] + dis[k][j]); } } } for (int i = 1; i <= n; i++) { int k; cin >> k; for (int j = 1; j <= k; j++) { int x; cin >> x; shield[x][i] = 1; } } for (int s = 1; s <= n; s++) { priority_queue<pair<int, int>, vector<pair<int, int> >, greater<pair<int, int> > > pq; memset(vis, 0, sizeof(vis)); for (int i = 1; i <= n; i++) { d[s][i] = INF; if (shield[s][i]) { for (int j = 1; j <= n; j++) { if (shield[s][j] && j != i) { d[s][i] = min(d[s][i], dis[i][j]); } } } else { d[s][i] = dis[s][i]; } } pq.push({d[s][s], s}); while (!pq.empty()) { int u = pq.top().second; pq.pop(); if (vis[u]) continue; vis[u] = 1; for (int i = head[u]; i != -1; i = edge[i].next) { int v = edge[i].to;

This code is implementing Dijkstra's algorithm with some modifications to find the shortest path between a source node and all other nodes in a graph. The modifications include the use of shielded edges, where certain edges are protected and cannot be used in the path, and the pre-calculation of all-pairs shortest path using Floyd-Warshall algorithm.

The code starts with defining some constants and data structures. `INF` is a large value used to represent infinity, `MAXN` and `MAXM` are the maximum number of nodes and edges in the graph, respectively. The `Edge` struct defines the properties of an edge in the graph including the destination node (`to`), the weight of the edge (`w`), and the index of the next edge in the adjacency list of the source node (`next`). An adjacency list is used to represent the graph, where `head` array stores the index of the first edge for each node.

The main function initializes some variables and reads the input. The first loop reads the edges of the graph and updates the adjacency list and the `dis` matrix which stores the shortest distance between any two nodes in the graph. The second loop reads the shielded edges for each node and updates the `shield` matrix accordingly.

The next loop uses Floyd-Warshall algorithm to pre-calculate the shortest path between all pairs of nodes in the graph and updates the `dis` matrix.

The last loop implements Dijkstra's algorithm with some modifications. For each source node `s`, it initializes the distance array `d` with the shortest distance to all other nodes considering the shielded edges. It uses a priority queue to select the node with the shortest distance and relaxes its neighbors, taking into account the shielded edges. The `vis` array is used to keep track of visited nodes to avoid loops.

Here's the complete code:

#include <bits/stdc++.h>
using namespace std;

const int INF = 0x3f3f3f3f;
const int MAXN = 25;
const int MAXM = 45;

struct Edge {
    int to, next, w;
} edge[MAXM];

int main() {
    int head[MAXN], cnt=0;
    int dis[MAXN][MAXN], vis[MAXN];
    int shield[MAXN][MAXN], d[MAXN][MAXN];
    int n, m;

    memset(dis, INF, sizeof(dis));
    memset(head, -1, sizeof(head));
    memset(shield, 0, sizeof(shield));

    cin >> n >> m;
    for (int i = 1; i <= m; i++) {
        int u, v, w;
        cin >> u >> v >> w;
        edge[cnt].to = v;
        edge[cnt].w = w;
        edge[cnt].next = head[u];
        head[u] = cnt++;
        dis[u][v] = min(dis[u][v], w);
    }

    for (int k = 1; k <= n; k++) {
        for (int i = 1; i <= n; i++) {
            for (int j = 1; j <= n; j++) {
                if (i == j) continue;
                dis[i][j] = min(dis[i][j], dis[i][k] + dis[k][j]);
            }
        }
    }

    for (int i = 1; i <= n; i++) {
        int k;
        cin >> k;
        for (int j = 1; j <= k; j++) {
            int x;
            cin >> x;
            shield[x][i] = 1;
        }
    }

    for (int s = 1; s <= n; s++) {
        priority_queue<pair<int, int>, vector<pair<int, int> >, greater<pair<int, int> > > pq;
        memset(vis, 0, sizeof(vis));
        for (int i = 1; i <= n; i++) {
            d[s][i] = INF;
            if (shield[s][i]) {
                for (int j = 1; j <= n; j++) {
                    if (shield[s][j] && j != i) {
                        d[s][i] = min(d[s][i], dis[i][j]);
                    }
                }
            } else {
                d[s][i] = dis[s][i];
            }
        }
        pq.push({d[s][s], s});
        while (!pq.empty()) {
            int u = pq.top().second;
            pq.pop();
            if (vis[u]) continue;
            vis[u] = 1;
            for (int i = head[u]; i != -1; i = edge[i].next) {
                int v = edge[i].to;
                int w = edge[i].w;
                if (shield[s][v]) {
                    for (int j = 1; j <= n; j++) {
                        if (shield[s][j] && j != v) {
                            d[s][v] = min(d[s][v], d[s][u] + dis[u][j] + w + dis[j][v]);
                        }
                    }
                } else {
                    d[s][v] = min(d[s][v], d[s][u] + w);
                }
                pq.push({d[s][v], v});
            }
        }
    }

    for (int i = 1; i <= n; i++) {
        int ans = INF;
        for (int j = 1; j <= n; j++) {
            if (shield[j][i]) continue;
            ans = min(ans, d[j][i]);
        }
        if (ans == INF) ans = -1;
        cout << ans << "\n";
    }

    return 0;
}

7-3 Score Processing 分数 10 作者 翁恺 单位 浙江大学 Write a program to process students score data. The input of your program has lines of text, in one of the two formats: Student's name and student id, as <student id>, <name>, and Score for one student of one course, as <student id>, <course name>, <marks>. Example of the two formats are: 3190101234, Zhang San 3190101111, Linear Algebra, 89.5 Comma is used as the seperator of each field, and will never be in any of the fields. Notice that there are more than one word for name of the person and name of the course. To make your code easier, the score can be treated as double. The number of the students and the number of the courses are not known at the beginning. The number of lines are not known at the beginning either. The lines of different format appear in no order. One student may not get enrolled in every course. Your program should read every line in and print out a table of summary in .csv format. The first line of the output is the table head, consists fields like this: student id, name, <course name 1>, <course name 2>, ..., average where the course names are all the courses read, in alphabet order. There should be one space after each comma. Then each line of the output is data for one student, in the ascended order of their student id, with score of each course, like: 3190101234, Zhang San, 85.0, , 89.5, , , 87.3 For the course that hasn't been enrolled, leave a blank before the comma, and should not get included in the average. The average has one decimal place. There should be one space after each comma. And the last line of the output is a summary line for average score of every course, like: , , 76.2, 87.4, , , 76.8 All the number output, including the averages have one decimal place. Input Format As described in the text above. Output Format As described in the text above. The standard output is generated by a program compiled by gcc, that the round of the first decimal place is in the "gcc way". Sample Input 3180111435, Operating System, 34.5 3180111430, Linear Algebra, 80 3180111435, Jessie Zhao 3180111430, Zhiwen Yang 3180111430, Computer Architecture, 46.5 3180111434, Linear Algebra, 61.5 3180111434, Anna Teng Sample Output student id, name, Computer Architecture, Linear Algebra, Operating System, average 3180111430, Zhiwen Yang, 46.5, 80.0, , 63.2 3180111434, Anna Teng, , 61.5, , 61.5 3180111435, Jessie Zhao, , , 34.5, 34.5 , , 46.5, 70.8, 34.

很好，这是一道关于学生成绩数据处理的编程题。下面是我的解答：

#include <iostream>
#include <vector>
#include <map>
#include <algorithm>
#include <iomanip>

using namespace std;

int main() {
    map<string, string> name_map; // 学生姓名字典
    map<string, vector<pair<string, double>>> score_map; // 学生成绩字典
    map<string, double> sum_map; // 课程成绩和字典
    map<string, int> cnt_map; // 课程成绩个数字典
    string line; // 输入的一行数据
    while (getline(cin, line)) {
        int pos1 = line.find(", "); // 第一个逗号的位置
        int pos2 = line.find(", ", pos1 + 2); // 第二个逗号的位置
        string id = line.substr(0, pos1); // 学生 ID
        string key = line.substr(pos2 + 2); // 课程名或学生姓名
        if (key.find('.') != string::npos) { // 如果是学生成绩
            double score = stod(key); // 成绩
            string course = line.substr(pos1 + 2, pos2 - pos1 - 2); // 课程名
            score_map[id].push_back(make_pair(course, score)); // 记录成绩
            sum_map[course] += score; // 累加成绩和
            cnt_map[course]++; // 记录个数
        } else {
            name_map[id] = key; // 记录学生姓名
        }
    }
    vector<string> courses; // 课程列表
    for (auto item : cnt_map) {
        courses.push_back(item.first);
    }
    sort(courses.begin(), courses.end()); // 课程按字母顺序排序
    cout << "student id, name, ";
    for (string course : courses) {
        cout << course << ", ";
    }
    cout << "average" << endl;
    for (auto item : score_map) {
        string id = item.first; // 学生 ID
        string name = name_map[id]; // 学生姓名
        cout << id << ", " << name << ", ";
        double sum = 0; // 成绩总和
        int cnt = 0; // 参加考试的课程数
        for (string course : courses) {
            bool found = false; // 是否参加考试
            for (auto score : item.second) {
                if (score.first == course) {
                    cout << fixed << setprecision(1) << score.second << ", ";
                    sum += score.second;
                    cnt++;
                    found = true;
                    break;
                }
            }
            if (!found) {
                cout << ", , ";
            }
        }
        if (cnt > 0) {
            cout << fixed << setprecision(1) << sum / cnt << endl;
        } else {
            cout << endl;
        }
    }
    cout << ", , ";
    for (string course : courses) {
        cout << fixed << setprecision(1) << (cnt_map[course] > 0 ? sum_map[course] / cnt_map[course] : 0) << ", ";
    }
    cout << endl;
    return 0;
}

这个程序的主要思路是使用四个字典来记录学生姓名、学生成绩、课程成绩和以及课程成绩个数，并且按照题目要求输出表格。

程序的详细注释如下：

1. 使用 `map<string, string> name_map` 记录每个学生的姓名，其中键为学生的 ID，值为学生的姓名。
2. 使用 `map<string, vector<pair<string, double>>> score_map` 记录每个学生的成绩，其中键为学生的 ID，值为包含课程名和成绩的一对 pair，使用 vector 来存储多个 pair。
3. 使用 `map<string, double> sum_map` 记录每门课程的成绩总和，其中键为课程名，值为成绩总和。
4. 使用 `map<string, int> cnt_map` 记录每门课程的成绩个数，其中键为课程名，值为成绩个数。
5. 使用 `getline(cin, line)` 读入每行输入，然后使用 `find()` 函数和 `substr()` 函数来解析每行输入。
6. 如果第二个逗号后面是数字，说明这是学生成绩，就把成绩和课程名记录在 `score_map`、`sum_map` 和 `cnt_map` 中。
7. 如果第二个逗号后面不是数字，说明这是学生姓名，就把学生姓名记录在 `name_map` 中。
8. 使用 `vector<string> courses` 记录所有参加考试的课程名，并且按字母顺序排序。
9. 使用 `cout` 输出表格头，先输出 `student id, name, `，然后按顺序输出所有课程名，最后输出 `average`。
10. 使用 `cout` 输出每个学生的成绩，先输出学生的 ID 和姓名，然后按顺序输出所有课程的成绩，如果某门课程没有参加考试，就留空，最后输出平均成绩。
11. 使用 `cout` 输出所有课程的平均成绩。

程序中使用了 `fixed` 和 `setprecision()` 函数来控制输出的小数点后一位。