Added year directories for advent of code

advent_of_code/2021/d9/main.cpp

@@ -0,0 +1,87 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+string file_name = "9.txt";
+// string file_name = "test.txt";
+
+int main(){
+    ios::sync_with_stdio(0);
+    cin.tie(0);
+
+    vector<vector<int>> heights;
+
+    ifstream file_stream;
+    file_stream.open(file_name);
+
+    if(file_stream.is_open()){
+        string line;
+
+        while(getline(file_stream, line)){
+            vector<int> line_input;
+
+            for(const char &c : line){
+                line_input.push_back(c - '0');
+            }
+
+            heights.push_back(line_input);
+        }
+    }
+
+    // Test input parsing
+    // for(auto v : heights){
+    //     for(auto i : v){
+    //         cout << i;
+    //     } cout << endl;
+    // } cout << endl;
+
+    size_t HEIGHT = heights.size() - 1, WIDTH = heights[0].size() - 1;
+
+    int result = 0;
+
+    for(size_t i = 0; i <= HEIGHT; ++i){
+        for(size_t j = 0; j <= WIDTH; ++j){
+            bool lowest = true;
+            int cur = heights[i][j];
+
+            // Check on corner cases (ha literally)
+            if(i != 0){
+                lowest &= cur < heights[i - 1][j];
+            }
+            if(i != HEIGHT){
+                lowest &= cur < heights[i + 1][j];
+            }
+
+            if(j != 0){
+                lowest &= cur < heights[i][j - 1];
+            }
+            if(j != WIDTH){
+                lowest &= cur < heights[i][j + 1];
+            }
+
+            if(lowest){
+                result += cur + 1;
+            }
+        }
+    }
+
+    cout << result << endl;
+
+    // For the second part we need to do some kind of scanning of all points line by line
+    // in which we need to make sure we don't scan points multiple times.
+    // Im thinking of something akin to line segment intersection with a scan line
+    // So keep track of which regions are currently present on the scan line
+    // One region can occur multiple times on the scane line,
+    // so we have to look into which events exist
+
+    // But now we have to keep track of the previous lines all the time as well,
+    // so it is not exactly the same as a scanning line thing
+
+    // I think this doesn't work, in the worst case I think you can have situations
+    // in which each points gets visited n times or n / 2 or something
+
+
+    cout << flush;
+
+    return 0;
+}