Tontti

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
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;
	}

	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]
				+ (forest[i - 1].at(j - 1) == '*' ? 1 : 0);
		}
	}

	int waysOfChoosing = 0;

	for (int i = 0; i < height; i++) {
		for (int j = 0; j < width; j++) {
			int minSl = 1;
			int maxSl = min(height - i, width - j);
			int midSl;
			while (minSl <= maxSl) {
				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) {
					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