[英]std::find on map not functioning properly and iterating through map's key and values
我目前正在嘗試訪問地圖的特定值元素,並遍歷該地圖以打印其特定元素的所有地圖鍵,但是在我在IDE(Eclipse)上進行調試時遇到了錯誤。這場斗爭? 過去幾天一直在努力尋找答案。
當調用std :: find時,它說,
'沒有匹配的成員函數來調用'find'
當使用迭代器遍歷地圖時,它說,
對二進制表達式無效的操作數(“ ostream”(又名“ basic_ostream”)和“ 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;
}
首先,我很好奇要知道您的程序應該執行的操作,這需要將int向量映射為chars向量的映射。 該地圖存儲成對的int向量和char向量,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
也許您想要一個std::map<int, char>
,它將一個int映射到一個char上,例如:
5 => m
2 => c
0 => a
如果您確實要打印出std::map<std::vector<int>, std::vector<char>>
,則需要像已經做的那樣遍歷鍵值對,然后通過循環分別打印出鍵向量和值向量。
例:
#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;
}
具有范圍for循環的更優雅的版本:
#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;
}
盡管最好的方法是使用<algorithm>
標頭中的函數,例如std::for_each
和lambdas為您完成所有循環。 我雖然不擅長這些東西。
對於您的查找操作,您有一個以std::vector<int>
作為鍵的映射,但是您為std::map::find
函數提供了一個整數。 如果您確實打算使用向量作為鍵的映射,則需要為函數提供向量,例如:
auto findResult = boardMap.find(std::vector<int>({8, 5, 2, 6}));
這將構造一個包含四個數字的向量,並將其賦予std::map::find
。
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