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pojcs101_M01088_ski.cpp

@@ -0,0 +1,76 @@
+#include <iostream>
+#include <vector>
+
+using namespace std;
+
+constexpr int DX[] = {0, 1, 0, -1};
+constexpr int DY[] = {1, 0, -1, 0};
+
+int path_length = 0;
+
+void log_grid(const vector<vector<int>>& grid, string name) {
+    for (const auto& row : grid) {
+        clog << name << ": ";
+        for (const auto& cell : row) {
+            clog << cell << " ";
+        }
+        clog << endl;
+    }
+}
+
+int dfs(const vector<vector<int>>& grid, const int x, const int y,
+        vector<vector<int>>& calculated_depths, const int _depth = 1) {
+    const unsigned int r = grid.size(), c = grid[0].size();
+
+    const int current_num = grid[x][y];
+    if (calculated_depths[x][y] > 0) { return calculated_depths[x][y] + _depth - 1; }
+
+    if (_depth + current_num <= path_length) {
+        // clog << "CUT " << x << "," << y << ":" << current_num << ", " << _depth << endl;
+        return -1;
+    } // 剪枝
+    // if (current_num == 1) { return _depth; }
+    // clog << x << "," << y << ":" << current_num << ", " << _depth << endl;
+
+    int best_depth = _depth;
+
+    for (int i = 0; i < 4; i++) {
+        const int nx = x + DX[i], ny = y + DY[i];
+        if (nx >= 0 && nx < r && ny >= 0 && ny < c && grid[nx][ny] < current_num) {
+            int next_depth = dfs(grid, nx, ny, calculated_depths, _depth + 1);
+            best_depth = max(best_depth, next_depth);
+        }
+    }
+    path_length = max(path_length, best_depth);
+    calculated_depths[x][y] = best_depth - _depth + 1;
+    return best_depth;
+}
+
+
+int main() {
+    ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    int r, c;
+    cin >> r >> c;
+
+    vector<vector<int>> grid(r, vector<int>(c));
+    vector<vector<int>> calculated_depths(r, vector<int>(c, 0));
+
+    for (int i = 0; i < r; i++) {
+        for (int j = 0; j < c; j++) {
+            cin >> grid[i][j];
+        }
+    }
+    for (int i = 0; i < r; i++) {
+        for (int j = 0; j < c; j++) {
+            dfs(grid, i, j, calculated_depths);
+            // clog << "---" << endl;
+            // log_grid(calculated_depths, "calculated_depths");
+            // clog << "---" << endl;
+        }
+    }
+    cout << path_length << endl;
+
+    return 0;
+}