我目前正在尝试访问我的 map 的特定值元素并遍历 map 以打印我的 map 的所有键及其特定元素但是当我在我的 IDE (Eclipse) 上调试时遇到错误关于如何我能战胜这场斗争吗?过去几天一直在寻找答案。
当调用 std::find 时,它说,
'no matching member function for call to 'find'
当通过映射使用迭代器到迭代器时,它说,
invalid operands to binary expression ('ostream' (aka 'basic_ostream') and 'const std::__1::vector >')
#include <iostream>
#include <vector>
#include <map>
#include <iterator>
#include <algorithm>
using namespace std;
int main() {
srand(time(NULL));
cout << "Enter # of rows: ";
int row;
cin >> row;
cout << "Enter # of columns: ";
int column;
cin >> column;
vector<vector<int> > numberBoard;
int startingIndex = 1;
for(int i = 0; i < row; i++){
vector<int> temp;
for(int j = 0; j < column; j++){
temp.push_back(startingIndex);
startingIndex++;
}
numberBoard.push_back(temp);
}
cout <<"Number Board:" << endl;
for(int i = 0; i < numberBoard.size(); i++){
for(int j = 0; j < numberBoard[i].size(); j++){
cout.width(5);
cout << numberBoard[i][j];
}
cout << endl;
}
vector<vector<char> > hiddenBoard(row, vector<char>(column));
// looping through outer vector vec
for (int i = 0; i < row; i++) {
// looping through inner vector vec[i]
for (int j = 0; j < column; j++) {
int random = rand()% 32 + 65;
(hiddenBoard[i])[j] = char(random);
//i*n + j;
}
}
cout << "\nBoard:" << endl;
for(int i = 0; i < hiddenBoard.size(); i++){
for(int j = 0; j < hiddenBoard[i].size(); j++){
cout.width(5);
cout << hiddenBoard[i][j];
}
cout << endl;
}
map<vector<int>, vector<char> > boardMap;
for(int i = 0; i < 20; i++){
boardMap[numberBoard[i]] = hiddenBoard[i];
}
//using std::find
int slotNum = 3;
map<vector<int>, vector<char> >::iterator it = boardMap.find(slotNum);
//trying to iterate through the map to print its corresponding key and value.
for(map<vector<int>, vector<char> >::iterator it = boardMap.begin(); it != boardMap.end(); it++){
cout << it->first << " => " << it->second << endl;
}
return 0;
}
最佳答案
首先,我很想知道您的程序应该做什么,这需要一个将整数 vector 映射到字符 vector 的映射。该映射存储成对的 int vector 和 char vector ,例如:
3 8 5 7 => c j i e
5 7 2 0 => l o x w
1 4 3 8 => k r u a
也许你想要一个 std::map<int, char>
它将一个 int 映射到一个 char,例如:
5 => m
2 => c
0 => a
如果你想打印出 std::map<std::vector<int>, std::vector<char>>
的内容,你需要像你已经在做的那样迭代键值对,然后用循环分别打印出键 vector 和值 vector 。
例子:
#include <iostream>
#include <map>
#include <vector>
int main()
{
std::map<std::vector<int>, std::vector<char>> boardMap; //declare and insert some values for testing
boardMap.insert(std::make_pair(std::vector<int>({ 8, 6, 2, 7 }), std::vector<char>({ 'o', 'd', 'a' })));
boardMap.insert(std::make_pair(std::vector<int>({ 4, 1, 0, 4 }), std::vector<char>({ 's', 'd', 'l' })));
for (auto it = boardMap.begin(); it != boardMap.end(); ++it)
{ //using auto is much better than writing std::map<std::vector<int>, std::vector<char>>::iterator every time
for (auto vecIt = it->first.begin(); vecIt != it->first.end(); ++vecIt) //output key vector
{
std::cout << *vecIt << ' ';
}
std::cout << "=>";
for (auto vecIt = it->second.begin(); vecIt != it->second.end(); ++vecIt) //output value vector
{
std::cout << ' ' << *vecIt;
}
std::cout << '\n';
}
return 0;
}
带有范围 for 循环的更优雅的版本:
#include <iostream>
#include <map>
#include <vector>
int main()
{
std::map<std::vector<int>, std::vector<char>> boardMap; //declare and insert some values for testing
boardMap.insert(std::make_pair(std::vector<int>({ 8, 6, 2, 7 }), std::vector<char>({ 'o', 'd', 'a' })));
boardMap.insert(std::make_pair(std::vector<int>({ 4, 1, 0, 4 }), std::vector<char>({ 's', 'd', 'l' })));
for (auto &keyValuePair : boardMap)
{ //using auto is much better than writing std::map<std::vector<int>, std::vector<char>>::iterator every time
for (auto &keyNum : keyValuePair.first) //output key vector
{
std::cout << keyNum << ' ';
}
std::cout << "=>";
for (auto &valueNum : keyValuePair.second) //output value vector
{
std::cout << ' ' << valueNum;
}
std::cout << '\n';
}
return 0;
}
尽管最好的方法是使用 <algorithm>
中的函数标题如 std::for_each
和 lambdas 为你做所有的循环。不过我不擅长这些。
对于您的查找操作,您有一张 map std::vector<int>
作为键,但你给 std::map::find
一个整数功能。如果你真的想要一个以 vector 作为键的映射,你需要给函数一个 vector ,比如:
auto findResult = boardMap.find(std::vector<int>({8, 5, 2, 6}));
这构建了一个包含四个数字的 vector 并将其提供给 std::map::find
.
关于c++ - std::find on map 无法正常运行并遍历 map 的键和值,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/50195725/