Sorting 2d array using std sort without vector

Question

#include <bits/stdc++.h>
using namespace std;

bool cmp(int *a, int *b){
 if(a[0] == b[0]) return a[1] < b[1];
 else return a[0] < b[0];
}
int main(){
 int arr[10][2];
 int n=10;

 for(int i=0;i<n;i++) scanf(" %d %d",&arr[i][0], &arr[i][1]);
 sort(arr, arr+n,cmp);
}

this code is just simple thing. your input is just like

and output should be like

simply you can think pair<int,int>.

let's say pair<int,int> to pair<a,b>.

i want to sort 'a' firstly. and if 'a' is same, then you should sort it by 'b'. (it's ascending sort)

so I have been trying to sort the array like this. but it doesn't work.

yea I know it's pretty easy if you use 'vector', but I don't want to use it. and I'm gonna use std::sort only.

of course you can't compile this because it's wrong.

I googled this problem but couldn't find anything. is there any way to solve this?

there is so many error code if you run this, so here's the error code that compiler brought directly to me.

1849 11 C:\Program Files (x86)\Dev-Cpp\MinGW64\lib\gcc\x86_64-w64-mingw32\4.9.2\include\c++\bits\stl_algo.h [Error] array must be initialized with a brace-enclosed initializer

C-style arrays are not assignable, `std::sort` can't work on non-assignable types. — Evg, Dec 30 '20 at 07:00
`std::array arr[10];` would solve this, otherwise use any type including own trivial struct. as long as assignment would be legal. You can't use `int arr[10][2];` because `arr[x] = arr[y]` is illegal — Swift - Friday Pie, Dec 30 '20 at 07:08
@user202729 mobile So bug. it doesn't show up nor for OP nor for others until someone posts answer — Swift - Friday Pie, Dec 30 '20 at 07:10
@Wolvthrough (apparently someone closed the question as duplicate. Read through the answers there) — user202729, Dec 30 '20 at 07:13
@user202729 dupe is fine, though solution offered in accepted answer there is meh. reinterpret-casting array isn't a way to do this properly. — Swift - Friday Pie, Dec 30 '20 at 07:15

Sorting 2d array using std sort without vector

0 Answers0