蓝桥杯2016年第七届真题-路径之谜(DFS)

#include<bits/stdc++.h>
using namespace std;
const int N = 21;
int topCount[N];
int leftCount[N];
bool vis[N][N] = {false};
int curTop[N] = {0};
int curLeft[N] = {0};
bool found = false;
class Node{
public:
    int x, y;
    Node(int i, int j) {
        x = i;
        y = j;
    }
};
int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};
bool check(int n) {
    for (int i = 0; i < n; i++) {
        if (topCount[i] != curTop[i] || leftCount[i] != curLeft[i]) {
            return false;
        }
    }
    return true;
}
void dfs(int x, int y, int n, vector<Node> &buf)
{
    if (curLeft[x] == leftCount[x] || curTop[y] == topCount[y]) {
        return;
    }
    curLeft[x]++;
    curTop[y]++;
    buf.push_back(Node(x, y));
    vis[x][y] = true;
    if (x == n-1 && y == n-1) {
        if (check(n)) {
            found = true;
            for (int i = 0; i < buf.size(); i++) {
                cout << n * buf[i].x + buf[i].y << " ";
            }
        }
    } else {
        for (int i = 0; i < 4; i++) {
            if (found) {
                return;
            }
            int tx = x + dx[i];
            int ty = y + dy[i];
            if (tx < 0 || tx >= n || ty < 0 || ty >= n || vis[tx][ty]) {
                continue;
            }
            dfs(tx, ty, n, buf);
        }
    }
    buf.pop_back();
    curTop[y]--;
    curLeft[x]--;
    vis[x][y] = false;
}
int main()
{
    int n;
    cin >> n;
    for (int i = 0; i < n; i++) {
        cin >> topCount[i];
    }
    for (int i = 0; i < n; i++) {
        cin >> leftCount[i];
    }
    vector<Node> buf;
    dfs(0, 0, n, buf);
    return 0;
}