hihoCoder1319 岛屿周长 (bfs)

#include <stdio.h>
#include<string.h>
#include <queue>
using namespace std;
const int maxn = 100+5;

int a[maxn][maxn];
bool con[maxn][maxn], vis[maxn][maxn];
int n, m;

struct Pos{
int x, y;
Pos(int x, int y):x(x), y(y){
}
};

const int dx[] = {0,0,1,-1};
const int dy[] = {1,-1,0,0};

bool isVis(int x, int y) {
if(x < 0 || y < 0 || x >= n || y >= m) return false;
return true;
}

void bfs(int x, int y) {
memset(vis, 0, sizeof(vis));
memset(con, 0, sizeof(con));
queue<Pos>Q;
vis[x][y] = true;
con[x][y] = true;
Q.push(Pos(x, y));
while(!Q.empty()) {
Pos p = Q.front();
Q.pop();
int x = p.x, y = p.y;
for(int i = 0; i < 4; i++) {
int px = x + dx[i];
int py = y + dy[i];
if(!isVis(px, py) || vis[px][py]) continue;
if(a[x][y] != a[px][py]) {
vis[px][py] = 1;
continue;
}
vis[px][py] = 1;
con[px][py] = 1;
Q.push(Pos(px, py));
}
}
}

int solve(int x, int y) {
bfs(x, y);
int ans = 0;
for(int i = 0; i < n; i++) {
for(int j = 0; j < m; j++) {
if(con[i][j]) {
for(int k = 0; k < 4; k++) {
int x = i + dx[k];
int y = j + dy[k];
if(!isVis(x, y) || !con[x][y]) {
ans++;
}
}
}
}
}
return ans;
}

int main() {
int x, y;
scanf("%d%d%d%d", &n, &m, &x, &y);
for(int i = 0; i < n; i++) {
for(int j = 0; j < m; j++) {
scanf("%d", &a[i][j]);
}
}
printf("%d\n", solve(x, y));
return 0;
}