每日一題之 頭條筆試題
阿新 • • 發佈:2018-12-14
思路
BFS,對每個出口標記走k步能到達的點,然後記錄每個點的距離。如果有某個點在之前的出口被標記走過且距離要大於當前的出口到這個點的距離的話,那麼就將該點的距離更新為離當前出口最近的距離。
#include <cstdio>
#include <iostream>
#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e3+7;
typedef long long ll;
struct Node
{
int x,y,s;
};
int dir[4][2] = { {0,1},{-1,0},{1,0},{0,-1}};
vector<int>G[maxn];
vector<Node>A;
vector<Node>res;
bool vis[maxn][maxn];
int dist[maxn][maxn];
void bfs(int x, int y, int k, int n, int m) {
queue<Node>q;
Node t;
t.x = x;
t.y = y;
t.s = 0;
q.push(t);
while(!q.empty()) {
Node now = q.front ();
q.pop();
for (int i = 0; i < 4; ++i) {
Node tmp;
tmp.x = now.x + dir[i][0];
tmp.y = now.y + dir[i][1];
tmp.s = now.s + 1;
if (vis[tmp.x][tmp.y] && dist[tmp.x][tmp.y] > tmp.s) {
vis[tmp.x][tmp.y] = 0;
}
//cout << tmp.x << " " << tmp.y << " " << endl;
if (tmp.x >= 0 && tmp.x < n && tmp.y >= 0 && tmp.y < m && tmp.s <= k && G[tmp.x][tmp.y] == 0 && !vis[tmp.x][tmp.y]) {
res.push_back(tmp);
vis[tmp.x][tmp.y] = 1;
dist[tmp.x][tmp.y] = tmp.s;
q.push(tmp);
}
}
}
}
int main() {
int k;
cin >> k;
char s;
int x;
int n = 0;
// !cin.eof()
//int t = 16;
while(!cin.eof()){
cin >> x;
s = getchar();
G[n].push_back(x);
if (s == '\n') ++n;
//G[n].push_back(x);
}
//int n = (int)G.size();
int m = (int)G[0].size();
//cout << m << endl;
for (int i = 0; i < n; ++i) {
for (int j = 0; j < (int)G[0].size(); ++j) {
vis[i][j] = 0;
dist[i][j] = maxn*maxn;
//cout << G[i][j] << " ";
if (G[i][j] == 1) {
Node tmp;
tmp.x = i;
tmp.y = j;
A.push_back(tmp);
dist[i][j] = 0;
//cout << i <<" "<< j << endl;
}
}
//cout << endl;
}
for (int i = 0; i < (int)A.size(); ++i) {
//cout << A[i].x << " " << A[i].y << endl;
bfs(A[i].x, A[i].y, k, n, m);
}
for (int i = 0; i < (int)res.size(); ++i) {
int x = res[i].x;
int y = res[i].y;
G[x][y] = 0;
}
for (int i = 0; i < n; ++i) {
for (int j = 0; j < m; ++j) {
if (G[i][j] == -1 || G[i][j] == 1) cout << "0";
else if (G[i][j] == 0 && vis[i][j] == 0) cout << "1";
else cout << G[i][j];
if (j != m-1) cout << ",";
else cout << endl;
}
}
return 0;
}
/*
3
0,-1,1,0
0,0,0,-1
0,-1,0,-1
1,-1,0,0
*/