Tontti

#include <iostream>
#include <algorithm>
#include <string>

int t[2001][2001];

struct myiter: std::iterator<std::forward_iterator_tag, int> {
	int x, y, w;
	myiter(int x, int y, int w): x(x), y(y), w(w) {
	}
	int operator* () {
		return t[x][y] + t[x-w][y-w] - t[x-w][y] - t[x][y-w];
	}
	bool operator != (myiter const& b) const {
		return w != b.w;
	}
	myiter const& operator ++() {
		++w;
		return *this;
	}
};

int main() {
	int n, m, x;
	long r = 0;
	std::cin >> n >> m >> x;
	for (int i = 1; i <= n; ++i) {
		std::string s;
		std::cin >> s;
		for (int j = 1; j <= m; ++j) {
			t[i][j] = t[i-1][j] + t[i][j-1] - t[i-1][j-1] + (s[j-1] == '*' ? 1 : 0);
			myiter i_begin(i, j, 1), i_end(i, j, std::min(i, j) + 1);
			std::pair<myiter, myiter> range = std::equal_range(i_begin, i_end, x);
			r += range.second.w - range.first.w;
		}
	}
	std::cout << r << std::endl;
}

Test 1

Subtask: 1

Verdict: ACCEPTED

Test 2

Subtask: 1

Verdict: ACCEPTED

Test 3

Subtask: 1

Verdict: ACCEPTED

Test 4

Subtask: 1

Verdict: ACCEPTED

Test 5

Subtask: 1

Verdict: ACCEPTED

Test 6

Subtask: 2

Verdict: ACCEPTED

Test 7

Subtask: 2

Verdict: ACCEPTED

Test 8

Subtask: 2

Verdict: ACCEPTED

Test 9

Subtask: 2

Verdict: ACCEPTED

Test 10

Subtask: 2

Verdict: ACCEPTED

Test 11

Subtask: 3

Verdict: ACCEPTED

Test 12

Subtask: 3

Verdict: ACCEPTED

Test 13

Subtask: 3

Verdict: ACCEPTED

Test 14

Subtask: 3

Verdict: ACCEPTED

Test 15

Subtask: 3

Verdict: ACCEPTED