Problem: 2062C - Cirno and Operations
Language: C++20 (GCC 13-64)

Previous submission (verdict: Wrong answer on test 2):
/* Gauri Jain
   2312004 */

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

#pragma comment(linker, "/stack:200000000")
#pragma GCC optimize("O1")
#pragma GCC optimize("O2")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx,avx2,fma")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")

#define endl "\n"
#define ll long long
#define EPS 1e-9
#define fl(a, b) for (int i = a; i < b; i++)
#define getarr(n) int* arr = new int[n]; fl(i, n) { cin >> arr[i]; }
#define getv(v, n) vector<int> v; fl(0, n) { int el; cin >> el; v.push_back(el); }
#define sortv(v) sort(v.begin(), v.end())

/* Debug Code */
void __print(int x) { cerr << x; }
void __print(long x) { cerr << x; }
void __print(long long x) { cerr << x; }
void __print(unsigned x) { cerr << x; }
void __print(unsigned long x) { cerr << x; }
void __print(unsigned long long x) { cerr << x; }
void __print(float x) { cerr << x; }
void __print(double x) { cerr << x; }
void __print(long double x) { cerr << x; }
void __print(char x) { cerr << '\'' << x << '\''; }
void __print(const char *x) { cerr << '\"' << x << '\"'; }
void __print(const string &x) { cerr << '\"' << x << '\"'; }
void __print(bool x) { cerr << (x ? "true" : "false"); }

template <typename A>
void __print(const A &x);
template <typename A, typename B>
void __print(const pair<A, B> &p);
template <typename T>
void __print(stack<T> s);
template <typename T>
void __print(queue<T> q);
template <typename T, typename... U>
void __print(priority_queue<T, U...> q);

template <typename A>
void __print(const A &x) {
    bool first = true;
    cerr << '{';
    for (const auto &i : x) {
        cerr << (first ? "" : ",");
        __print(i);
        first = false;
    }
    cerr << '}';
}

template <typename A, typename B>
void __print(const pair<A, B> &p) {
    cerr << '(';
    __print(p.first);
    cerr << ',';
    __print(p.second);
    cerr << ')';
}

template <typename T>
void __print(stack<T> s) {
    vector<T> debugVector;
    while (!s.empty()) {
        T t = s.top();
        debugVector.push_back(t);
        s.pop();
    }
    reverse(debugVector.begin(), debugVector.end());
    __print(debugVector);
}

template <typename T>
void __print(queue<T> q) {
    vector<T> debugVector;
    while (!q.empty()) {
        T t = q.front();
        debugVector.push_back(t);
        q.pop();
    }
    __print(debugVector);
}

template <typename T, typename... U>
void __print(priority_queue<T, U...> q) {
    vector<T> debugVector;
    while (!q.empty()) {
        T t = q.top();
        debugVector.push_back(t);
        q.pop();
    }
    __print(debugVector);
}

void _print() { cerr << "]\n"; }

template <typename Head, typename... Tail>
void _print(const Head &H, const Tail &...T) {
    __print(H);
    if (sizeof...(T))
        cerr << ", ";
    _print(T...);
}

bool isInteger(double num) {
    return floor(num) == num;
}

void print(vector<int> &arr) {
    for (int i = 0; i < arr.size(); i++) {
        cout << arr[i] << " ";
    }
    cout << endl;
}

string decimalToBinary(int n) {
    if (n == 0) return "0";
    string binary = "";
    while (n > 0) {
        binary += std::to_string(n % 2);
        n /= 2;
    }
    reverse(binary.begin(), binary.end());
    return binary;
}
#ifndef ONLINE_JUDGE
#define debug(...) cerr << "Line: " << __LINE__ << " [" << #__VA_ARGS__ << "] = [", _print(__VA_ARGS__)
#else
#define debug(...)
#endif
void solve(){
    int n; cin >> n;
    vector<int> a(n);
    for(int i=0; i<n; i++) cin >> a[i];
    ll sum = 0, maxi = LLONG_MIN;
    if(n == 1){
        cout << a[0] << endl;
        return;
    }
    for(int i=0; i<n; i++){
        for(int j=0; j<n-i; j++){
            sum += a[j];
            if(j+1<n)a[j] = a[j+1] - a[j];
        }
        maxi = max(maxi, abs(sum));
        sum = 0;
    }
    cout << maxi << endl;
    return;
}
int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    int t;
    cin >> t;
    while (t--) {
        solve();
    }
    return 0;
}


Submission (verdict: Wrong answer on test 2):
/* Gauri Jain
   2312004 */

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

#pragma comment(linker, "/stack:200000000")
#pragma GCC optimize("O1")
#pragma GCC optimize("O2")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx,avx2,fma")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")

#define endl "\n"
#define ll long long
#define EPS 1e-9
#define fl(a, b) for (int i = a; i < b; i++)
#define getarr(n) int* arr = new int[n]; fl(i, n) { cin >> arr[i]; }
#define getv(v, n) vector<int> v; fl(0, n) { int el; cin >> el; v.push_back(el); }
#define sortv(v) sort(v.begin(), v.end())

/* Debug Code */
void __print(int x) { cerr << x; }
void __print(long x) { cerr << x; }
void __print(long long x) { cerr << x; }
void __print(unsigned x) { cerr << x; }
void __print(unsigned long x) { cerr << x; }
void __print(unsigned long long x) { cerr << x; }
void __print(float x) { cerr << x; }
void __print(double x) { cerr << x; }
void __print(long double x) { cerr << x; }
void __print(char x) { cerr << '\'' << x << '\''; }
void __print(const char *x) { cerr << '\"' << x << '\"'; }
void __print(const string &x) { cerr << '\"' << x << '\"'; }
void __print(bool x) { cerr << (x ? "true" : "false"); }

template <typename A>
void __print(const A &x);
template <typename A, typename B>
void __print(const pair<A, B> &p);
template <typename T>
void __print(stack<T> s);
template <typename T>
void __print(queue<T> q);
template <typename T, typename... U>
void __print(priority_queue<T, U...> q);

template <typename A>
void __print(const A &x) {
    bool first = true;
    cerr << '{';
    for (const auto &i : x) {
        cerr << (first ? "" : ",");
        __print(i);
        first = false;
    }
    cerr << '}';
}

template <typename A, typename B>
void __print(const pair<A, B> &p) {
    cerr << '(';
    __print(p.first);
    cerr << ',';
    __print(p.second);
    cerr << ')';
}

template <typename T>
void __print(stack<T> s) {
    vector<T> debugVector;
    while (!s.empty()) {
        T t = s.top();
        debugVector.push_back(t);
        s.pop();
    }
    reverse(debugVector.begin(), debugVector.end());
    __print(debugVector);
}

template <typename T>
void __print(queue<T> q) {
    vector<T> debugVector;
    while (!q.empty()) {
        T t = q.front();
        debugVector.push_back(t);
        q.pop();
    }
    __print(debugVector);
}

template <typename T, typename... U>
void __print(priority_queue<T, U...> q) {
    vector<T> debugVector;
    while (!q.empty()) {
        T t = q.top();
        debugVector.push_back(t);
        q.pop();
    }
    __print(debugVector);
}

void _print() { cerr << "]\n"; }

template <typename Head, typename... Tail>
void _print(const Head &H, const Tail &...T) {
    __print(H);
    if (sizeof...(T))
        cerr << ", ";
    _print(T...);
}

bool isInteger(double num) {
    return floor(num) == num;
}

void print(vector<int> &arr) {
    for (int i = 0; i < arr.size(); i++) {
        cout << arr[i] << " ";
    }
    cout << endl;
}

string decimalToBinary(int n) {
    if (n == 0) return "0";
    string binary = "";
    while (n > 0) {
        binary += std::to_string(n % 2);
        n /= 2;
    }
    reverse(binary.begin(), binary.end());
    return binary;
}
#ifndef ONLINE_JUDGE
#define debug(...) cerr << "Line: " << __LINE__ << " [" << #__VA_ARGS__ << "] = [", _print(__VA_ARGS__)
#else
#define debug(...)
#endif
void solve(){
    int n; cin >> n;
    vector<int> a(n);
    for(int i=0; i<n; i++) cin >> a[i];
    ll sum = 0, maxi = LLONG_MIN;
    if(n == 1){
        cout << a[0] << endl;
        return;
    }
    for(int i=0; i<n; i++){
        for(int j=0; j<n-i; j++){
            sum += a[j];
            if(j+1<n)a[j] = a[j] - a[j+1];
        }
        maxi = max(maxi, abs(sum));
        sum = 0;
    }
    cout << maxi << endl;
    return;
}
int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    int t;
    cin >> t;
    while (t--) {
        solve();
    }
    return 0;
}