CompetitiveProgramming/Arithmetic Rectangle.cpp at main · MariaChrysafis/CompetitiveProgramming · GitHub

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#include<bits/stdc++.h>
usingnamespacestd;
vector<int> solver1 (vector<int> v) { //find first smaller one to left
 stack<int> st;
 vector<int> val(v.size());
for (int i = 0; i < v.size(); i++) {
while (!st.empty() && v[st.top()] >= v[i]) {
 st.pop();
 }
if (st.empty()) {
 val[i] = -1;
 } else {
 val[i] = st.top();
 }
 st.push(i);
 }
return val;
}

vector<int> solver2 (vector<int> v) { //find first smaller one to right
 stack<int> st;
 vector<int> val(v.size());
for (int i = v.size() - 1; i >= 0; i--) {
while (!st.empty() && v[st.top()] >= v[i]) {
 st.pop();
 }
if (st.empty()) {
 val[i] = v.size();
 } else {
 val[i] = st.top();
 }
 st.push(i);
 }
return val;
}

intgetter (vector<int> v) {
if (v.size() <= 2) return v.size();
 vector<int> a;
for (int i = 1; i < v.size(); i++) {
 a.push_back(v[i] - v[i - 1]);
 }
int myMax = 2;
int cur = 2;
for (int i = 1; i < a.size(); i++) {
if (a[i] == a[i - 1]) cur++, myMax = max(myMax, cur);
else cur = 2;
 }
return myMax;
}

intget_grid (vector<vector<int> >& arr, int i, int j) {
return (int64_t)arr[i][j] + (int64_t)arr[i + 1][j + 1] - (int64_t)arr[i + 1][j] - (int64_t)arr[i][j + 1];
}
voidsolve() {
int n, m;
 cin >> n >> m;
 vector<vector<int> > arr(n);
int myMax = 0;
for (int i = 0; i < n; i++) {
 arr[i].resize(m);
for (int j = 0; j < m; j++) {
 cin >> arr[i][j];
 }
 }
for (int i = 0; i < n; i++) {
 vector<int> v;
for (int j = 0; j < m; j++) {
 v.push_back(arr[i][j]);
 }
 myMax = max(myMax, getter(v));
 }
for (int j = 0; j < m; j++) {
 vector<int> v;
for (int i = 0; i < n; i++) {
 v.push_back(arr[i][j]);
 }
 myMax = max(myMax, getter(v));
 }
 vector<vector<int> > d(n - 1);
for (int i = 0; i < n - 1; i++) {
 d[i].resize(m - 1);
 }
for (int i = (int)d.size() - 1; i >= 0; i--) {
for (int j = 0; j < (int)d[i].size(); j++) {
if (i == (int)d.size() - 1 || get_grid(arr, i + 1, j) != get_grid(arr, i, j)) {
 d[i][j] = 1;
 } else {
 d[i][j] = d[i + 1][j] + 1;
 }
 }
 }
for (int i = 0; i < d.size(); i++) {
 vector<int> v1 = solver1(d[i]);
 vector<int> v2 = solver2(d[i]);
 vector<int> right(d[0].size());
int prev = -1;
for (int j = (int)d[0].size() - 1; j >= 0; j--) {
if (j == (int)d[0].size() - 1) prev = j;
elseif (get_grid(arr, i, j) != get_grid(arr, i, j + 1)) prev = j;
 right[j] = prev;
 }
 prev = -1;
for (int j = 0; j < d[0].size(); j++) {
if (j == 0) prev = 0;
elseif (get_grid(arr, i, j) != get_grid(arr, i, j - 1)) prev = j;
int res = (min(right[j], v2[j] - 1) - max(prev, v1[j] + 1) + 2) * ((int)d[i][j] + 1);
 myMax = max(myMax, res);
 }
 }
 cout << myMax << '\n';
}
intmain() {
ios_base::sync_with_stdio(false);
 cin.tie(NULL);
int t;
 cin >> t;
while (t--) {
solve();
 }
}