题目

思路：

#include <bits/stdc++.h>
using namespace std;
#define int long long
#define pb push_back
#define fi first
#define se second
#define lson p << 1
#define rson p << 1 | 1
const int maxn = 1e6 + 5, inf = 1e18, maxm = 4e4 + 5, base = 397;
// const int mod = 1e9 + 7;
const __int128 mod = 212370440130137957LL;
const int N = 1e6;
// int a[505][505];
int a[maxn];
bool vis[maxn];
int n, m;
string s;

struct Node{
    int val, id;
    bool operator<(const Node &u)const{
        return val < u.val;
    }
}c[maxn];

int d[maxn];

void solve(){
    int res = 0;
    int k, q;
    int p;
    cin >> n;
    for(int i = 1; i <= n; i++){
        cin >> a[i];
    }
    for(int i = 2; i <= n; i++){
        d[i] = a[i] - a[i - 1];
    }
    if(n % 2 == 1){
        cout << "Yes\n";
        return;
    }
    int sum[2] = {0};
    for(int i = 2; i <= n; i++){
        sum[i % 2] += d[i];
    }
    if(sum[0] >= 0){
        cout << "Yes\n";
    }
    else{
        cout << "No\n";
    }
}
    
signed main(){
    ios::sync_with_stdio(0);
    cin.tie(0);
    
    int T = 1;
    cin >> T;
    while (T--)
    {
        solve();
    }
    return 0;
}