我正在尝试遍历数组，但是具有多行的播放器编号要么不累积其第二个实例，要么获得奇怪的编号（最后一个）。
PlayerHitsWalksOuts
1 2 2 2
19 0 5 7
2 0 5 7
18 4 2 0
4 3 3 6
12 2 2 2
7 0 0 9 // should be 7 0 0 6 , because two 7 0 0 3 lines in input file
8 1 4 1
10 2 2 2
3 3 3 6
11 6 0 0
17 4 2 0
9 3 2 1
由于我确定我正确编写了main（），所以我迷失了为什么它不起作用。我认为该类文件也是正确的。将索引设置为0时，出现“分段错误（核心已转储）”。
#include "Player.h"
#include <iostream>
#include <fstream>
int findNumber(const Player p[], int numPlayers, int playerNumber);
void displayArray(Player team[], int team_size);
int main()
{
fstream fin("baseball.txt");
const int LIST_LENGTH = 20;
int number = 0,
hits,
walks,
outs,
playerIndex,
index = -1,
teamSize = 0;
cout << "This program tracks a baseball player's number "
<< "and their\nnumber of hits, walks, and outs for "
<< "each games in a season.\n";
Player team[LIST_LENGTH];
while (!fin.eof())
{
fin >> number >> hits >> walks >> outs;
playerIndex = findNumber(team, teamSize, number);
if (playerIndex == -1)
{
teamSize++;
index++;
team[index].setNumber(number);
team[index].setHits(hits);
team[index].setWalks(walks);
team[index].setOuts(outs);
}
else
{
team[index].setHits(hits + team[index].getHits());
team[index].setWalks(walks + team[index].getWalks());
team[index].setOuts(outs + team[index].getOuts());
}
displayArray(team, teamSize);
fin.close();
}
}
int findNumber(const Player p[], int numPlayers, int playerNumber)
{
int i;
for (i = 0; i < numPlayers; i++)
{
if (p[i].getNumber() == playerNumber)
return i;
}
return -1;
}
void displayArray(Player team[], int team_size)
{
cout << "\n\nPlayer\tHits\tWalks\tOuts\n"
<< "------\t----\t-----\t----\n";
for (int i = 0; i < team_size; i++)
{
cout << team[i] << endl;
}
}
player.h：
{#include "Player.h"
#include <iostream>
#include <iomanip>
using namespace std;
Player::Player()
{
Number = Hits = Walks = Outs = 0;
}
int Player::getNumber() const
{
return Number;
}
int Player::getHits() const
{
return Hits;
}
int Player::getWalks() const
{
return Walks;
}
int Player::getOuts() const
{
return Outs;
}
void Player::setNumber(int n)
{
Number = n;
}
void Player::setHits(int h)
{
Hits = h;
}
void Player::setWalks(int w)
{
Walks = w;
}
void Player::setOuts(int o)
{
Outs = o;
}
const Player& Player::operator=(const Player & p)
{
if (this != &p)
{
Number = p.Number;
Hits = p.Hits;
Walks = p.Walks;
Outs = p.Outs;
}
return *this;
}
ostream& operator<<(ostream& out, const Player & p)
{
out << setw(2) << p.Number << "\t"
<< setw(2) << p.Hits << "\t"
<< setw(2) << p.Walks << "\t"
<< setw(2) << p.Outs;
return out;
}
答案 0 :(得分：1)
我不会对Why is iostream::eof inside a loop condition considered wrong?讲太多，因为在显示的代码中这无关紧要。使用输入操作本身作为循环的条件：
while (fin >> number >> hits >> walks >> outs)
{
在应该从中读取的循环中关闭输入文件：
while ( /* ... */ ) { // ... playerIndex = findNumber(team, teamSize, number); if (playerIndex == -1) // ... displayArray(team, teamSize); fin.close(); // <<========================= here. Remove that. }
您将index与playerIndex混淆了：
// here you try to find the player by its number in the team playerIndex = findNumber(team, teamSize, number); if (playerIndex == -1) { teamSize++; index++; team[index].setNumber(number); // index could be ok in that case, // ... // but why use an extra variable } // when teamSize (before it gets in- else // crementet) is the same? { // here you should be using the index that you found with // findNumber() instead of index. So replace index with playerIndex team[index].setHits(hits + team[index].getHits()); team[index].setWalks(walks + team[index].getWalks()); team[index].setOuts(outs + team[index].getOuts()); }
如果您实现了operator+=，则它的代码可能会更短，更容易阅读，Player是一个接受值的构造函数，并且可能是类#include <cstdlib> // EXIT_FAILURE
#include <fstream>
#include <iostream>
#include <iomanip>
#include <algorithm> // std::find, std::copy
#include <iterator> // std::ostream_iterator
class Player {
int Number = 0;
int Hits = 0;
int Walks = 0;
int Outs = 0;
public:
Player() = default;
Player(int number, int hits, int walks, int outs)
: Number {number},
Hits {hits},
Walks {walks},
Outs {outs}
{}
Player& operator+=(Player const &other)
{
Hits += other.Hits;
Walks += other.Walks;
Outs += other.Outs;
return *this;
}
int getNumber() const { return Number; }
friend std::istream& operator>>(std::istream& in, Player &p)
{
int number, hits, walks, outs;
if (in >> number >> hits >> walks >> outs)
p = Player{ number, hits, walks, outs };
return in;
}
friend std::ostream& operator<<(std::ostream& out, Player const &p)
{
return out << std::setw(2) << p.Number << "\t" << std::setw(2) << p.Hits << "\t"
<< std::setw(2) << p.Walks << "\t" << std::setw(2) << p.Outs;
}
};
bool operator==(Player const &lhs, int Number) noexcept
{
return lhs.getNumber() == Number;
}
std::size_t findNumber(Player const *team, std::size_t numPlayers, int playerNumber)
{
return std::find(team, team + numPlayers, playerNumber) - team;
}
void displayArray(Player *team, std::size_t numPlayers)
{
std::cout << "\n\nPlayer\tHits\tWalks\tOuts\n------\t----\t-----\t----\n";
std::copy(team, team + numPlayers, std::ostream_iterator<Player>{ std::cout , "\n" });
}
int main()
{
constexpr std::size_t LIST_LENGTH{ 20 };
Player team[LIST_LENGTH];
std::size_t teamSize{};
std::ifstream fin("test.txt");
if (!fin.is_open()) {
std::cerr << "Couldn't open the players list for reading :(\n\n";
return EXIT_FAILURE;
}
Player p;
while (teamSize < LIST_LENGTH && fin >> p)
{
auto playerIndex{ findNumber(team, teamSize, p.getNumber()) };
if (playerIndex == teamSize)
team[teamSize++ ] = p;
else team[playerIndex] += p;
}
displayArray(team, teamSize);
}
的流提取运算符：
{{1}}