OJ Board

Posted: **Fri Jan 26, 2007 10:11 am**

I'm so awkward using in STL. When I implemented 2D array sort in C, I used bubble sort.
But I want to know how can I sort 2D array in STL sort().

For example,

Code: Select all

// before sort
string data[3][2] = { {"cab","hello"}, {"cba","world"}, {"abc","haha"}};

// After sort 
string data[3][2] = { {"abc","haha"}, {"cab","hello"}, {"cba","world"}};

In this array, I want sort to use first elements of data array.
How can I wrote comp() function for my sort() method??

Code: Select all

// I'll use like this
sort( &data[0], data[3], comp );

Posted: **Mon Jan 29, 2007 10:51 am**

hello
maximum time i solve this type of problem by this way

Code: Select all

#include <stdio.h>
#include <algorithm>
#include <string>
#include <vector>

using namespace std;

struct Node {
	vector <string> S;
};

vector <Node> V;

bool cmp(Node A, Node B) {
	int i;
	for (i = 0; i < A.S.size() && i < B.S.size(); i++) {
		if (A.S[i] < B.S[i])
			return true;
		if (A.S[i] > B.S[i])
			return false;
	}
	if (A.S.size() < B.S.size())
		return true;
	return false;
}

int main() {

	int i, j;

	V.clear();
	Node A;

	A.S.clear();
	A.S.push_back("cab"); A.S.push_back("hello"); A.S.push_back("abc");
	V.push_back(A);

	A.S.clear();
	A.S.push_back("cba"); A.S.push_back("world");
	V.push_back(A);

	A.S.clear();
	A.S.push_back("abc"); A.S.push_back("haha");
	V.push_back(A);

	A.S.clear();
	A.S.push_back("abc"); A.S.push_back("haha"); A.S.push_back("world");
	V.push_back(A);

	A.S.clear();
	A.S.push_back("cba"); A.S.push_back("abc");
	V.push_back(A);

	A.S.clear();
	A.S.push_back("cab"); A.S.push_back("hello"); A.S.push_back("a");
	V.push_back(A);

	sort(V.begin(), V.end(), cmp);
	for (i = 0; i < V.size(); i++) {
		for (j = 0; j < V[i].S.size(); j++) {
			printf("%s ", V[i].S[j].c_str());
		}
		printf("\n");
	}
	return 0;
}

Thankx
MAP

Posted: **Sat Feb 03, 2007 9:18 am**

I would rather like to put the 2D array in a 1D string array or in a vector<string> and then sort.
in that case the comp function would be:

Code: Select all

bool comp(string a, string b){
  return a<b;
}

for loops in comp function seems more costly then: 2D -> 1D -> sorted 1D -> again 2D

Posted: **Thu Jun 21, 2007 1:28 pm**

I think you cannot use two dimensional array in sort function:

Code: Select all

int a[3][2] = {{1, 2}, {3, 4}, {5, 6}};
sort(a, a + 3); // Syntax eror

for solving this problem you must use vector:

Code: Select all

#include <iostream>
#include <string>
#include <algorithm>
#include <vector>

using namespace std;

void print(vector<string> data[])
{
	int i, j;
	for (i = 0; i < 3; i++)
	{
		for (j = 0; j < 2; j++)
			cout << data[i][j] << ' ';
		cout << endl;
	}
}

int main()
{
	string data[3][2] = { {"cab","hello"}, {"cba","world"}, {"abc","haha"}};
	vector< string > v[3] =
	{vector< string >(data[0], data[0] + 2),
	vector< string >(data[1], data[1] + 2),
	vector< string >(data[2], data[2] + 2)};
	print(v);
	cout << endl;
	sort(v, v + 3);
	print(v);

	return 0;
}

OJ Board

2D string array for STL sort

2D string array for STL sort