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#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using pi = pair<int, int>;
using vpi = vector<pi>;
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
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};
//pretty printing
template<typename K, typename V>
void printm(const map<K, V> &mp) {
cerr << "{" << endl;
for (auto p : mp) {
cerr << " { " << p.first << " : " << p.second << " }\n";
}
cerr << "}" << endl;
}
template<typename T>
void printv(const vector<T> &v) {
cerr << "[";
for (int i = 0; i < v.size(); i++) {
if (i == v.size() - 1) {
cerr << v[i];
} else {
cerr << v[i] << ", ";
}
}
cerr << "]\n";
}
template<typename T>
void printvv(const vector<vector<T>> &v) {
cerr << "[\n";
for (auto &vec : v) {
cout << " ";
printv(vec);
}
cerr << "]\n";
}
void print() {
cerr << "\n";
}
template<typename T, typename... TS>
void print(T val, TS... vals) {
cerr << val << " ";
print(vals...);
}
/* 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 solve() {
int n, c;
cin >> n >> c;
vector<int> a(n);
for (int i = 0; i < n; i++) {
cin >> a[i];
}
vector<int> s(n), e(n);
multiset<int> ms;
for (int i = 0; i < n; i++) {
s[i] = a[i] + i + 1;
e[i] = a[i] + n - i;
ms.insert(s[i]);
}
vector<pair<int, int>> x(n);
for (int i = 0; i < n; i++) {
if (s[i] <= e[i]) {
x[i] = {s[i], -s[i]};
} else {
x[i] = {e[i], s[i]};
}
}
sort(x.begin(), x.end());
int ans = 0;
bool found = false;
while (ans < n && c - x[ans].first >= 0) {
c -= x[ans].first;
ms.erase(ms.find(abs(x[ans].second)));
if (x[ans].second < 0) {
found = true;
}
ans += 1;
}
if (found) {
cout << ans << '\n';
} else {
while (*ms.begin() > c && ans >= 0) {
c += x[ans - 1].first;
ms.insert(abs(x[ans - 1].second));
ans -= 1;
}
cout << ans + 1 << '\n';
}
}
int main () {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int tt;
cin >> tt;
while(tt--) {
solve();
}
}
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