CP_Codeforces/1941B.cpp at main · overthinker036/CP_Codeforces · GitHub

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

int main () {
	ll t; cin >> t;

	while (t--) {
	  ll n; cin >> n;

	  ll arr[n];

	  for (ll i = 0; i < n; i++) {
	  	cin >> arr[i];
	  }

	  for (ll i = 1; i < n-1; i++) {
	  	if (arr[i] == 0) {
	  		continue;
	  	} else {
	  		ll tg = 0;
	  	if (arr[i-1] == arr[i+1]) {
	  	  if (arr[i] >= 0) {
	  	  	tg = arr[i-1];

	  	    arr[i-1] = 0;
	  	    arr[i+1] = 0;

	  	    arr[i] -= (2*tg);
	  	  } else {
	  	  	tg = arr[i-1];

	  	    arr[i-1] = 0;
	  	    arr[i+1] = 0;

	  	    arr[i] += (2*tg);
	  	  }

	  	} else if (arr[i+1] < arr[i-1]) {
	  		if (arr[i] >= 0) {
	  			tg = arr[i+1];

	  	  	arr[i+1] = 0;
	    		arr[i-1] -= tg;

	    		arr[i] -= 2*tg;
	  		} else {
	  			tg = arr[i+1];

	  		  arr[i+1] = 0;
	  	  	arr[i-1] += tg;

	    		arr[i] += 2*tg;
	  		}
	  	} else {
	  		if (arr[i] >= 0) {
	  			tg = arr[i-1];

	  		  arr[i-1] = 0;
	  	  	arr[i+1] -= tg;

	  	  	arr[i] -= 2*tg;
	  		} else {
	  			tg = arr[i-1];

	  	  	arr[i-1] = 0;
	    		arr[i+1] += tg;

	    		arr[i] += 2*tg;
	  		}
	  	}
	  	}
	  }

	  bool ok = true;

	  for (auto it : arr) {
	  	if (it != 0) {
	  		ok = false;
	  		break;
	  	}
	  }

	  if (ok) {
	  	cout << "YES" << endl;
	  } else {
	  	cout << "NO" << endl;
	  }
	}
}