BOJ 16234: 인구 이동

작성일

https://www.acmicpc.net/problem/16234

  • 3월동안 210문제 풀기 (6/210)
  • DFS 두번 돌리는 문제, DFS 한번 돌릴때 합이랑 개수 구하고, 두번째에서 기록하면 됨.
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#include <bits/stdc++.h>
using namespace std;
int N, L, R;
vector<vector<int>> arr, visit;

const int dx[4] = {0,0,1,-1};
const int dy[4] = {1,-1,0,0};
inline bool bound(int x, int y) {
  return x >= 0 && x < N && y >= 0 && y < N;
}
void go(int x, int y, int& cnt, int& num) {
  visit[x][y] = 1;
  cnt = 1, num = arr[x][y];
  for(int i = 0; i < 4; i++) {
    int nx = x + dx[i];
    int ny = y + dy[i];
    if(!bound(nx,ny) || visit[nx][ny]) continue;
    int diff = abs(arr[x][y] - arr[nx][ny]);
    if(diff < L || diff > R) continue;
    int subCnt, subNum;
    go(nx,ny, subCnt, subNum);
    cnt += subCnt, num += subNum;
  }
}

void fill(int x, int y, int v) {
  if(v != -1) arr[x][y] = v;
  visit[x][y] = 2;
  for(int i = 0; i < 4; i++) {
    int nx = x + dx[i];
    int ny = y + dy[i];
    if(!bound(nx,ny) || visit[nx][ny] != 1) continue;
    fill(nx,ny,v);
  }
}


int main() {
  scanf("%d %d %d", &N, &L, &R);
  arr = vector<vector<int>>(N, vector<int>(N));
  visit = vector<vector<int>>(N, vector<int>(N));
  for(int i =0; i < N; i++)
    for(int j = 0; j < N; j++)
      scanf("%d", &arr[i][j]);
  int gen = 0;
  while(1) {
    bool flag = 0;
    for(int i =0; i < N; i++)
      for(int j = 0; j < N; j++)
        if(!visit[i][j]) {
          int cnt, num;
          go(i,j,cnt,num);
          if(cnt > 1) {
            fill(i,j,num/cnt);
            flag = true;
          } else fill(i,j,-1);
        }
    if(!flag) break;
    gen++;

    for(int i =0; i < N; i++)
      for(int j = 0; j < N; j++)
        visit[i][j] = 0;
  }
  printf("%d",gen);
}