RECHEND - Editorial

editorial
, ,
44
1 Like
45

Thanku very much

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46

Getting wrong answer for the following. Please help me with this.

from collections import defaultdict


def solve():
    for _ in range(int(input())):
        n = int(input())

        freq_1 = defaultdict(lambda: 0)
        freq_2 = defaultdict(lambda: 0)
        for __ in range(n):
            x, y = map(int, input().split())
            if x + y <= n + 1:
                freq_1[x + y] += 1
            else:
                freq_2[n - x + n - y + 1] += 1

        for key in freq_1.keys():
            if key - 1 == freq_1[key]:
                print('NO')
                return

        for key in freq_2.keys():
            if key == freq_2[key]:
                print('NO')
                return

        print('YES')


solve()
47

Consider the test input:

2
2
1 2
2 1
2
1 2
2 1
48

Why my code gives a WA?

#include<bits/stdc++.h>
#define Endl ‘\n’
#define pb push_back
#define ll long long int
#define fi(x,n) for(ll i=x;i<n;i++)
using namespace std;
void solve()
{
ll n;
cin>>n;

vector < pair<ll,ll> > vp;
map < pair<ll,ll> ,ll > m;
fi(0,n)
{
    ll x,y;
    cin>>x>>y;
    m[{x,y}]=1;
    vp.pb({x,y});
}

ll res=0;
map < pair<ll,ll>,ll > vis;
fi(0,n)
{
    ll x=vp[i].first,y=vp[i].second;
    if(!vis[{x,y}])
    {
        ll len=1,tempx=x-1,tempy=y+1;
        while(m[{tempx,tempy}])
        {
            vis[{tempx,tempy}]=1;
            len++;
            tempx--;tempy++;
        }

        tempx=x+1;tempy=y-1;
        while(m[{tempx,tempy}])
        {
            vis[{tempx,tempy}]=1;
            len++;
            tempx++;tempy--;
        }

        if(len==1+min(x-1,n-y)+min(n-x,y-1))
            res=1;
    }
}

if(res)
    cout<<"NO";
else
    cout<<"YES";
cout<<Endl;

}
int main()
{
ll t;
scanf("%lld",&t);
while(t–)
solve();

return 0;

}

49

Nice approach!
What category would you put this question in?
was it adhoc or just observation

50

I’d say it was just an observation based problem.

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