Submission #75084643

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Source Code Expand

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

#define int long long 

const int N=2e5+5;

bool st;
int t,n,a[N],m,c[N],d[N];
bool ed;

signed main() {
	ios::sync_with_stdio(false);
	cin.tie(0),cout.tie(0);
	cin>>t;
	while(t--) {
		cin>>n>>m;a[n+1]=0;
		for(int i=1;i<=n;i++) cin>>a[i];
		int x=n/2;
		int sum=0;
		for(int i=1;i<=x;i++) c[i]=((a[i]-a[n+1-i])%m+m)%m;
		for(int i=1;i<=x;i++) d[i]=(c[i-1]-c[i]+m)%m;
		d[x+1]=c[x];
		sort(d+1,d+x+2);
		for(int i=1;i<=x+1;i++) sum+=d[i];
		int temp=sum/m;
		for(int i=0;i<temp;i++) sum-=d[x+1-i];
		cout<<sum<<'\n';
	}
	return 0;
}

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