1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
|
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;
using vpii = vector<pii>;
using vi = vector<int>;
using vll = vector<long long>;
using mpii = map<int, int>;
using mpll = map<ll, ll>;
using db = long double;
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define lb lower_bound
#define ub upper_bound
#define make_unique(x) \
sort(all((x))); \
(x).resize(unique(all((x))) - (x).begin())
#define ceil(a, b) ((a) + (b)-1) / (b)
const int mod = (int)1e9 + 7;
const db pi = acos((db)-1);
const int dx[4]{1, 0, -1, 0};
const int dy[4]{0, 1, 0, -1};
#ifdef LOCAL
#include "debug.h"
#else
#define dbg(...) 42
#endif
/* stuff you should look for:
---------------------------
* special cases (n=1?)
* int overflow, array bounds
* do smth instead of nothing and stay organized
* WRITE STUFF DOWN
* DON'T GET STUCK ON ONE APPROACH
*/
void apply(vi &v, int idx, int times) {
v[idx] -= 2 * times;
v[idx - 1] -= times;
v[idx + 1] -= times;
}
void solve() {
int n;
cin >> n;
vi v(n);
for (auto &x : v) {
cin >> x;
}
for (int i = 0; i < n - 2; i++) {
int times = v[i];
if (times < 0) {
cout << "NO\n";
return;
}
apply(v, i + 1, times);
}
if (all_of(all(v), [](int x) { return x == 0; })) {
cout << "YES\n";
} else {
cout << "NO\n";
}
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int tt;
cin >> tt;
while (tt--) {
solve();
}
}
|