标签：sts BMI ssi div mes lan count VID union
In a N x N grid composed of 1 x 1 squares, each 1 x 1 square consists of a /, \, or blank space. These characters divide the square into contiguous regions.
(Note that backslash characters are escaped, so a \ is represented as "\\".)
Return the number of regions.
我的DFS解法。
Runtime: 32 ms, faster than 12.39% of C++ online submissions for Regions Cut By Slashes.
#include <string>
#include <iostream>
#include <vector>
using namespace std;
int dirs[8][2] = {{0,1},{0,-1},{1,0},{-1,0},{1,1},{1,-1},{-1,1},{-1,-1}};
class Solution {
public:
int regionsBySlashes(vector<string>& grid) {
size_t n = grid.size();
vector<vector<int>> mtx(4*n, vector<int>(4*n, 0));
for(int i=0; i<n; i++){
for(int j=0; j<n; j++){
if(grid[i][j] == ‘/‘){
mtx[4*i][4*j+3] = 1;
mtx[4*i+1][4*j+2] = 1;
mtx[4*i+2][4*j+1] = 1;
mtx[4*i+3][4*j] = 1;
}else if(grid[i][j] == ‘\\‘){
mtx[4*i][4*j] = 1;
mtx[4*i+1][4*j+1] = 1;
mtx[4*i+2][4*j+2] = 1;
mtx[4*i+3][4*j+3] = 1;
}
}
}
int ret = 0;
for(int i=0; i<4*n; i++){
for(int j=0; j<4*n; j++){
if(mtx[i][j] == 0) ret++;
dfs(mtx, i, j);
}
}
return ret;
}
void dfs(vector<vector<int>>& mtx, int x, int y){
size_t n = mtx.size();
if(x < 0 || x >= n || y < 0 || y >= n || mtx[x][y] != 0) return ;
mtx[x][y] = -1;
for(int i=0; i<4; i++){
int newx = x+dirs[i][0];
int newy = y+dirs[i][1];
if(newx >= 0 && newy >= 0 && newx < n && newy < n && i >= 4){
if(mtx[newx][y] == 1 && mtx[x][newy] == 1) continue;
}
dfs(mtx, newx, newy);
}
}
};
网上的unionfound解法。
class Solution {
public:
int count, n;
vector<int> f;
int regionsBySlashes(vector<string>& grid) {
n = grid.size();
count = n * n * 4;
for (int i = 0; i < n * n * 4; ++i)
f.push_back(i);
for (int i = 0; i < n; ++i) {
for (int j = 0; j < n; ++j) {
if (i > 0) uni(g(i - 1, j, 2), g(i, j, 0));
if (j > 0) uni(g(i , j - 1, 1), g(i , j, 3));
if (grid[i][j] != ‘/‘) {
uni(g(i , j, 0), g(i , j, 1));
uni(g(i , j, 2), g(i , j, 3));
}
if (grid[i][j] != ‘\\‘) {
uni(g(i , j, 0), g(i , j, 3));
uni(g(i , j, 2), g(i , j, 1));
}
}
}
return count;
}
int find(int x) {
if (x != f[x]) {
f[x] = find(f[x]);
}
return f[x];
}
void uni(int x, int y) {
x = find(x); y = find(y);
if (x != y) {
f[x] = y;
count--;
}
}
int g(int i, int j, int k) {
return (i * n + j) * 4 + k;
}
};
LC 959. Regions Cut By Slashes
标签：sts BMI ssi div mes lan count VID union
原文地址：https://www.cnblogs.com/ethanhong/p/10193441.html
