P43164 | Treasures in a map (5)

#include <iostream>
#include <vector>
#include <queue>
#include <map>

using namespace std;

const vector<int> DI = {1,0,-1,0};
const vector<int> DJ = {0,1,0,-1};
typedef vector<vector<char>> GRAPH;
typedef pair<pair<int,int>,int> VL;

bool in_range(int i,  int j, int n, int m) {
	return 0 <= i and 0 <= j and i < n and j < m;
}

int main() {
	int n, m; cin >> n >> m;
	GRAPH g(n,vector<char>(m));
	for (int i = 0; i < n; ++i) {
		for (int j = 0; j < m; ++j) {
			cin >> g[i][j];
		}
	}
	int counter = 0;
	int a, b; cin >> a >> b; --a; --b;
	map<int,int> s;
	VL aux; aux.first.first = a; aux.first.second = b; aux.second = 0; bool r = in_range(a,b,n,m);
	queue<VL> q; q.push(aux);
	while (not q.empty() and r) {
		int ui = q.front().first.first; int uj = q.front().first.second;
		int d = q.front().second;
		q.pop();
		if (g[ui][uj] != 'v' and g[ui][uj] != 'X') {
			if (g[ui][uj] == 't') {
				if (s.find(d) == s.end()) {
					s.insert(make_pair(d,1));
				} else {
					map<int,int>::iterator it = s.find(d);
					it -> second = it->second+1;
				}
				++counter;
			}
			g[ui][uj] = 'v';
			for (int i = 0; i < 4; ++i) {
				VL v;
				v.first.first = ui + DI[i];
				v.first.second = uj + DJ[i];
				if (in_range(v.first.first, v.first.second, n, m)) {
					v.second = d + 1;
					q.push(v);
				}
			}
		}
	}

	map<int,int>::const_iterator it = s.end();
	if (counter < 2) cout << "we cannot reach two or more treasures" << endl;
	else {
		--it;
		if (it -> second >= 2) cout << "second maximum distance: " << it -> first << endl;
		else {
			--it;
			cout << "second maximum distance: " << it -> first << endl;
		}
	}
}