Tontti

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <cmath>
using namespace std;
 
int main() {
	ios::sync_with_stdio(false);
 
	int height;
	cin >> height;
 
	int width;
	cin >> width;
 
	int idealAmountOfTrees;
	cin >> idealAmountOfTrees;
 
	vector<string> forest;
	forest.resize(height);
 
	for (int i = 0; i < height; i++) {
		cin >> forest[i];
	}
 
	vector<vector<int> > sums;
	sums.resize(height + 1);
	for (int i = 0; i <= height; i++) {
		sums[i].resize(width + 1);
	}
 
	for (int i = 0; i <= height; i++) {
		sums[i][0] = 0;
	}
 
	for (int j = 1; j <= width; j++) {
		sums[0][j] = 0;
	}
 
	int amountOfTrees = 0;
	for (int i = 1; i <= height; i++) {
		for (int j = 1; j <= width; j++) {
			sums[i][j] = sums[i - 1][j] - sums[i - 1][j - 1] + sums[i][j - 1];
			if (forest[i - 1].at(j - 1) == '*') {
				sums[i][j]++;
				amountOfTrees++;
			}
		}
	}
 
	if (amountOfTrees < idealAmountOfTrees) {
		cout << "0" << endl;
	}
	else {
 
		int waysOfChoosing = 0;
		const int firstMSL = (int)ceil(sqrt(idealAmountOfTrees));
 
		for (int i = 0; i < height; i++) {
			int previousSidelength = 0;
			for (int j = 0; j < width; j++) {
				int minSl = firstMSL;
				int maxSl = min(height - i, width - j);
				int midSl;
				bool first = true;
 
				while (minSl <= maxSl) {
					if (first && previousSidelength != 0 && previousSidelength <= maxSl) {
						midSl = previousSidelength;
						first = false;
					}
					else {
						midSl = (minSl + maxSl) / 2;
					}
					int treesInSquare = sums[i + midSl][j + midSl] - sums[i + midSl][j] - sums[i][j + midSl] + sums[i][j];
					if (treesInSquare == idealAmountOfTrees) {
						previousSidelength = midSl;
						waysOfChoosing++;
						int l1 = midSl - 1;
						while (l1 >= minSl && (sums[i + l1][j + l1] - sums[i + l1][j] - sums[i][j + l1] + sums[i][j]) == idealAmountOfTrees) {
							waysOfChoosing++;
							l1--;
						}
						int l2 = midSl + 1;
						while (l2 <= maxSl && (sums[i + l2][j + l2] - sums[i + l2][j] - sums[i][j + l2] + sums[i][j]) == idealAmountOfTrees) {
							waysOfChoosing++;
							l2++;
						}
						break;
					}
					else if (treesInSquare < idealAmountOfTrees) {
						minSl = midSl + 1;
					}
					else {
						maxSl = midSl - 1;
					}
				}
			}
		}
 
		cout << waysOfChoosing << endl;
 
	}
	return 0;
}

Test 1

Group: 1

Verdict: ACCEPTED

Test 2

Group: 1

Verdict: ACCEPTED

Test 3

Group: 1

Verdict: ACCEPTED

Test 4

Group: 1

Verdict: ACCEPTED

Test 5

Group: 1

Verdict: ACCEPTED

Test 6

Group: 2

Verdict: ACCEPTED

Test 7

Group: 2

Verdict: ACCEPTED

Test 8

Group: 2

Verdict: ACCEPTED

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 2

Verdict: ACCEPTED

Test 11

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 12

Group: 3

Verdict: ACCEPTED

Test 13

Group: 3

Verdict: ACCEPTED

Test 14

Group: 3

Verdict: ACCEPTED

Test 15

Group: 3

Verdict: ACCEPTED