added week9

Author: VitamintK

Week9/2017-11-30/A.cpp

@@ -0,0 +1,57 @@
+//https://open.kattis.com/contests/cgq7ia/problems/coast
+#include<bits/stdc++.h>
+
+using namespace std;
+
+int n, m;
+vector<vector<int> > grid;
+int ans = 0;
+
+void dfs(int r, int c){
+    vector<int> dr = {-1, 0, 1, 0};
+    vector<int> dc = {0, 1, 0, -1};
+    for(int i = 0; i < 4; i++){
+        //explore all 4 immediate neighbors
+        int nr = r + dr[i];
+        int nc = c + dc[i];
+        if(nr >= 0 && nr <= n+1 && nc >= 0 && nc <= m+1){
+            if(grid[nr][nc] == 0){
+                grid[nr][nc] = 2;
+                //if it's water, then we DFS there
+                //but we'll set it to 2 so that we know it's been visited
+                dfs(nr, nc);
+            } else if(grid[nr][nc] == 1){
+                //if it's 1, then we've found an edge to land.  so we increment ans by 1.
+                ans++;
+            }
+        }
+    }
+}
+
+int main(){
+    cin >> n >> m;
+    grid.push_back(vector<int>(m+2, 0));
+    for(int i = 1; i < n+1; i++){
+        grid.push_back(vector<int>(m+2, 0));
+        for(int j = 1; j < m+1; j++){
+            char a;
+            cin >> a;
+            if(a == '1'){
+                grid[i][j] = 1;
+            } else {
+                grid[i][j] = 0;
+            }
+        }
+    }
+    grid.push_back(vector<int>(m+2));
+    //debug code to print out the grid:
+    // for(int i = 0; i < n+2; i++){
+    //     for(int j = 0; j < m+2; j++){
+    //         cout << grid[i][j];
+    //     } cout << endl;
+    // }
+    grid[0][0] = 2;
+    dfs(0, 0);
+    cout << ans << endl;
+    return 0;
+}