Problem: 2060D - Subtract Min Sort
Language: C++20 (GCC 13-64)

Previous submission (verdict: Wrong answer on test 2):
#include <bits/stdc++.h>

#define fi first 
#define se second 
#define pb push_back
#define pf push_front
#define ppb pop_back
#define ppf pop_front
#define ld long double
#define ll long long int
#define Int unsigned int 
#define Long unsigned long long int
#define eliminate(x, y) (x).erase(remove(all(x), (y)), (x).end())
#define make_unique(x) sort(all(x)), (x).erase(unique(all(x)), (x).end());
#define all_range(x) (x).begin(), (x).begin()
#define All(x) (x).rbegin(), (x).rend()
#define all(x) (x).begin(), (x).end()
#define sz(x) (int)x.size()
#define newl cerr << '\n'

using namespace std;
template<class T> using Set = unordered_set<T>;
template<class T> using min_heap = priority_queue<T, vector<T>, greater<T>>;  
template<class T, class U> using Map = unordered_map<T, U>;
 
template<typename T>void prd(const T& x);
template<typename T, typename U>void prd(const pair<T, U>& val);
template<typename T, typename... Args>void prd(const T& val, Args... args);
template<typename... Args>void debug(Args... args);
template<typename T>void debug(const set<T>& c);
template<typename T>void debug(const vector<T>& c);
template<typename T>void debug(const vector<vector<T>> &c);
template<typename K, typename V>void debug(const map<K, V>& c);

const int MOD = 1e9 + 7;
const int mod = 998244353;
const int INF = 2e9 + 7;
const ll INFL = 2e18 + 7;
const double EPS = 1e-9;

void FastIO();

int main(){
 
    FastIO();
    int t,n; cin >> t;
    while(t--){
        cin >> n;
        vector<int> A(n);

        for(int &a : A) cin >> a;

        bool valid1 = 1, valid2 = 1;

        for(int i = n - 2; i >= 0; i -= 2)
            if(A[i] > A[i + 1])    
                valid1 = 0;

        for(int i = n - 3; i >= 0; i -= 2)
            if(A[i] > A[i + 1])
                valid2 = 0;

        cout << (valid1 || valid2 ? "YES" : "NO") << '\n';
    }

    return 0;
}
 
void FastIO(){ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);}
template<typename T> void prd(const T& x){cerr<<x;}
template<typename T, typename U>void prd(const pair<T, U>& val){cerr<<"(";prd(val.fi);cerr<<", ";prd(val.se);cerr<<")";}
template<typename T, typename... Args>void prd(const T& val, Args... args){prd(val);cerr<<", ";prd(args...);}
template<typename... Args> void debug(Args... args){cerr << "["; prd(args...);cerr<<"]\n";}
template<typename T> void debug(const set<T>& c){cerr<<'[';bool cm=0;for(const auto& st:c){if(cm)cerr<<", ";prd(st);cm=1;}cerr<<"]\n";}
template<typename T> void debug(const vector<T>& c){cerr<<'[';bool cm=0;for(const auto& v:c){if(cm)cerr<<", ";prd(v);cm=1;}cerr<<"]\n";}
template<typename T> void debug(const vector<vector<T>> &c){for(const auto &v: c)debug(v);cerr<<'\n';}
template<typename K, typename V> void debug(const map<K, V>& c){cerr<<'[';bool cm=0;for(auto[k, v]:c){if(cm)cerr<<", ";cerr<<'[';prd(k);cerr <<", ";prd(v);cerr<<']';cm = 1;}cerr<<"]\n";}


Submission (verdict: Accepted):
#include <bits/stdc++.h>

#define fi first 
#define se second 
#define pb push_back
#define pf push_front
#define ppb pop_back
#define ppf pop_front
#define ld long double
#define ll long long int
#define Int unsigned int 
#define Long unsigned long long int
#define eliminate(x, y) (x).erase(remove(all(x), (y)), (x).end())
#define make_unique(x) sort(all(x)), (x).erase(unique(all(x)), (x).end());
#define all_range(x) (x).begin(), (x).begin()
#define All(x) (x).rbegin(), (x).rend()
#define all(x) (x).begin(), (x).end()
#define sz(x) (int)x.size()
#define newl cerr << '\n'

using namespace std;
template<class T> using Set = unordered_set<T>;
template<class T> using min_heap = priority_queue<T, vector<T>, greater<T>>;  
template<class T, class U> using Map = unordered_map<T, U>;
 
template<typename T>void prd(const T& x);
template<typename T, typename U>void prd(const pair<T, U>& val);
template<typename T, typename... Args>void prd(const T& val, Args... args);
template<typename... Args>void debug(Args... args);
template<typename T>void debug(const set<T>& c);
template<typename T>void debug(const vector<T>& c);
template<typename T>void debug(const vector<vector<T>> &c);
template<typename K, typename V>void debug(const map<K, V>& c);

const int MOD = 1e9 + 7;
const int mod = 998244353;
const int INF = 2e9 + 7;
const ll INFL = 2e18 + 7;
const double EPS = 1e-9;

void FastIO();

int main(){
 
    FastIO();
    int t,n; cin >> t;
    while(t--){
        cin >> n;
        vector<int> A(n);

        for(int &a : A) cin >> a;

        bool ans = 1;

        for(int i = 0, m; i + 1 < n; i++){
            if(A[i] > A[i + 1])
                ans = 0;
            A[i + 1] -= min(A[i], A[i + 1]);
        }

        cout << (ans ? "YES" : "NO") << '\n';
    }

    return 0;
}
 
void FastIO(){ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);}
template<typename T> void prd(const T& x){cerr<<x;}
template<typename T, typename U>void prd(const pair<T, U>& val){cerr<<"(";prd(val.fi);cerr<<", ";prd(val.se);cerr<<")";}
template<typename T, typename... Args>void prd(const T& val, Args... args){prd(val);cerr<<", ";prd(args...);}
template<typename... Args> void debug(Args... args){cerr << "["; prd(args...);cerr<<"]\n";}
template<typename T> void debug(const set<T>& c){cerr<<'[';bool cm=0;for(const auto& st:c){if(cm)cerr<<", ";prd(st);cm=1;}cerr<<"]\n";}
template<typename T> void debug(const vector<T>& c){cerr<<'[';bool cm=0;for(const auto& v:c){if(cm)cerr<<", ";prd(v);cm=1;}cerr<<"]\n";}
template<typename T> void debug(const vector<vector<T>> &c){for(const auto &v: c)debug(v);cerr<<'\n';}
template<typename K, typename V> void debug(const map<K, V>& c){cerr<<'[';bool cm=0;for(auto[k, v]:c){if(cm)cerr<<", ";cerr<<'[';prd(k);cerr <<", ";prd(v);cerr<<']';cm = 1;}cerr<<"]\n";}