#1200. [2016NOIP福建夏令营]迷宫 [40pts]

https://sjzezoj.com/submission/46119

S2OJ/1200/1200.cpp

@@ -0,0 +1,52 @@
+#include <iostream>
+#include <vector>
+
+using std::cin;
+using std::cout;
+using std::endl;
+
+const long long mod = 281474976710656;
+
+int n;
+long long ans;
+char g[505][505];
+
+void dfs1(int, int, std::vector<int>);
+long long dfs2(int, int, std::vector<int>, int, int, std::vector<int>);
+
+int main() {
+    cin >> n;
+    for (int i = 1; i <= n; i++) {
+        cin >> g[i] + 1;
+    }
+    dfs1(1, 1, std::vector<int>());
+    cout << ans << endl;
+    return 0;
+}
+
+void dfs1(int x, int y, std::vector<int> s) {
+    if (x < 1 || x > n || y < 1 || y > n) return;
+    s.push_back(g[x][y] - 'A');
+    if (x + y == n + 1) {
+        ans = (ans + dfs2(n, n, std::vector<int>(), x, y, s)) % mod;
+        return;
+    }
+    dfs1(x + 1, y, s);
+    dfs1(x, y + 1, s);
+}
+
+long long dfs2(
+    int x,
+    int y,
+    std::vector<int> s,
+    int lx,
+    int ly,
+    std::vector<int> t) {
+    if (x < lx || x > n || y < ly || y > n) return 0;
+    s.push_back(g[x][y] - 'A');
+    long long res = 0;
+    if (x == lx && y == ly && s == t) return 1;
+    res += dfs2(x - 1, y, s, lx, ly, t);
+    res += dfs2(x, y - 1, s, lx, ly, t);
+    return res;
+}