Question

How to search a vector for specific value and get the index in C++

Answer 1

#include <iostream>
#include <vector>

using std::vector;
using std::cout;
using std::endl;

int main()
{
	vector<int> vec = { 1, 3, 8, 23, 88, 12, 99, 7 };

	auto pos = std::find(vec.begin(), vec.end(), 88);

	if (pos != vec.end()) {
		cout << "found in index: " << std::distance(vec.begin(), pos) << endl;
	}
	else {
		cout << "not found" << endl;
	}
}


/*
run:

found in index: 4

*/

 

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Answer 2

#include <iostream>
#include <vector>

using std::vector;
using std::cout;
using std::endl;

int main()
{
	vector<int> vec = { 1, 3, 8, 23, 88, 12, 99, 7 };

	ptrdiff_t pos = find(vec.begin(), vec.end(), 12) - vec.begin();

	if (pos < vec.size()) {
		cout << "found in index: " << pos << endl;
	}
	else {
		cout << "not found" << endl;
	}
}


/*
run:

found in index: 5

*/

 

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Answer 3

#include <iostream>
#include <vector>

using std::vector;
using std::cout;
using std::endl;

int main()
{
	vector<int> vec = { 1, 3, 8, 23, 88, 12, 99, 7 };

	ptrdiff_t pos = distance(vec.begin(), find(vec.begin(), vec.end(), 8));

	if (pos < vec.size()) {
		cout << "found in index: " << pos << endl;
	}
	else {
		cout << "not found" << endl;
	}
}


/*
run:

found in index: 2

*/

 

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