Judge - 1237 : 2보 전진을 위한 1보 후퇴 C++

출처 : https://judge.koreatech.ac.kr/problem.php?id=1237

 

두가지 방법으로 풀었다.

 

1. 실제로 2보 전진, 1보 후퇴하는식으로 bfs탐색으로 해결

2. 그냥 bfs탐색을 하면서 parent를 이용해서 경로를 저장한 뒤, 도착지점에서 출발지점으로 2보전진 1보후퇴

 

출발지점이 벽인 경우를 처음에 고려를 안해서 계속 틀리다보니 고민을 계속 하다가 두가지 방법이 나오게 되었다.

출발지점이 벽인 경우를 고려하면 둘 다 맞는 답이다.

 

#include <iostream>
#include <string>
#include <vector>
#include <math.h>
#include <algorithm>
#include <utility>
#include <stack>
#include <queue>
#include <math.h>
#include <set>
#include <map>
#include <list>
#include <unordered_map>
#include <unordered_set>
#include <iomanip>
#include <limits.h>
 
using namespace std;
using int64 = long long;
 
int n;
 
struct location {
    int row;
    int col;
    int cnt;
};
 
int dRow[4] = { -1,0,1,0 };
int dCol[4] = { 0,1,0,-1 };
 
vector<vector<int>> board;
vector<vector<bool>> found;
 
pair<int, int> start = { 0,0 };
pair<int, int> target;
 
int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
 
    cin >> n;
    board = vector<vector<int>>(n, vector<int>(n));
    found = vector<vector<bool>>(n, vector<bool>(n, false));
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            cin >> board[i][j];
        }
    }
    target = { n - 1,n - 1 };
 
    if (board[start.first][start.second] == 0 || board[target.first][target.second] == 0) {
        cout << "-1" << "\n";
        return 0;
    }
 
    queue<location> q;
    q.push({ start.first,start.second,0 });
    found[start.first][start.second] = true;
 
    while (!q.empty()) {
        auto curr = q.front();
        q.pop();
 
        bool isReached = false;
 
        int ans = INT_MAX;
 
        for (int i = 0; i < 4; i++) {
            int nextRow = curr.row + dRow[i];
            int nextCol = curr.col + dCol[i];
            int nextCnt = curr.cnt + 1;
            if (nextRow < 0 || nextRow >= n) continue;
            if (nextCol < 0 || nextCol >= n) continue;
            if (board[nextRow][nextCol] == 0) continue;
            if (found[nextRow][nextCol]) continue;
            if (nextRow == target.first && nextCol == target.second) {
                isReached = true;
                ans = min(ans, nextCnt);
            }
            for (int j = 0; j < 4; j++) {
                int nnextRow = nextRow + dRow[j];
                int nnextCol = nextCol + dCol[j];
                int nnextCnt = nextCnt + 1;
                if (nnextRow < 0 || nnextRow >= n) continue;
                if (nnextCol < 0 || nnextCol >= n) continue;
                if (board[nnextRow][nnextCol] == 0) continue;
                if (found[nnextRow][nnextCol]) continue;
                if (nnextRow == target.first && nnextCol == target.second) {
                    isReached = true;
                    ans = min(ans, nnextCnt);
                }
                q.push({ nextRow,nextCol,nnextCnt + 1 });
                found[nextRow][nextCol] = true;
            }
        }
 
        if (isReached) {
            cout << ans << "\n";
            return 0;
        }
    }
    cout << -1 << "\n";
}

 

#include <iostream>
#include <string>
#include <vector>
#include <math.h>
#include <algorithm>
#include <utility>
#include <stack>
#include <queue>
#include <math.h>
#include <set>
#include <map>
#include <list>
#include <unordered_map>
#include <unordered_set>
#include <iomanip>
#include <limits.h>
 
using namespace std;
using int64 = long long;
 
int n;
 
int dRow[4] = { -1,0,1,0 };
int dCol[4] = { 0,1,0,-1 };
 
vector<vector<int>> board;
vector<vector<bool>> found;
vector<vector<pair<int, int>>> parent;
 
pair<int, int> start = { 0,0 };
pair<int, int> target;
 
int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
 
    cin >> n;
    board = vector<vector<int>>(n, vector<int>(n));
    found = vector<vector<bool>>(n, vector<bool>(n, false));
    parent = vector<vector<pair<int, int>>>(n, vector<pair<int, int>>(n));
 
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            cin >> board[i][j];
        }
    }
    target = { n - 1,n - 1 };
 
    if (board[start.first][start.second] == 0 || board[target.first][target.second] == 0) {
        cout << "-1" << "\n";
        return 0;
    }
 
    queue<pair<int, int>> q;
    q.push({ start.first,start.second});
    found[start.first][start.second] = true;
    parent[start.first][start.second] = start;
 
    bool isPossible = false;
 
    while (!q.empty()) {
        auto curr = q.front();
        q.pop();
        if (curr.first == target.first && curr.second == target.second) {
            isPossible = true;
            break;
        }
 
        for (int i = 0; i < 4; i++) {
            int nextRow = curr.first + dRow[i];
            int nextCol = curr.second + dCol[i];
            if (nextRow < 0 || nextRow >= n) continue;
            if (nextCol < 0 || nextCol >= n) continue;
            if (board[nextRow][nextCol] == 0) continue;
            if (found[nextRow][nextCol]) continue;
            q.push({ nextRow,nextCol });
            found[nextRow][nextCol] = true;
            parent[nextRow][nextCol] = { curr.first,curr.second };
        }
    }
 
    if (!isPossible) {
        cout << "-1" << "\n";
        return 0;
    }
 
    pair<int, int> curr = target;
    int cnt = 0;
 
    while (true) {
 
        if (curr == start) break;
 
        cnt++;
        pair<int, int> _parent = parent[curr.first][curr.second];
        if (_parent == start) break;
 
        cnt++;
        pair<int, int> _pparent = parent[_parent.first][_parent.second];
        if (_pparent == start) break;
 
        cnt++;
        curr = _parent;
    }
    cout << cnt << "\n";
}