[solved] boj25682

HwangJinHa/BOJ/20231026 - 20231030 [ 태호의 장점이 뭔 지 알아? ]/boj25682_체스판다시칠하기2.java

@@ -0,0 +1,78 @@
+package study10월5주차월;
+
+import java.io.BufferedReader;
+import java.io.InputStreamReader;
+import java.util.StringTokenizer;
+
+public class boj25682_체스판다시칠하기2 {
+    static int n, m, k;
+    static char[][] chess;
+    static int[][] sum;
+    public static void main(String[] args) throws Exception {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        StringTokenizer st;
+
+        st = new StringTokenizer(br.readLine());
+        n = Integer.parseInt(st.nextToken());
+        m = Integer.parseInt(st.nextToken());
+        k = Integer.parseInt(st.nextToken());
+
+        chess = new char[n][];
+        sum = new int[n][m];
+        for (int i = 0; i < n; i++) {
+            chess[i] = br.readLine().toCharArray();
+            for (int j = 0; j < m; j++) {
+                sum[i][j] = ((i + j)%2 == 0 ? 'B' : 'W') == chess[i][j]? 0 : 1;
+                setSum(i, j);
+            }
+        }
+        int ans = k * k;
+        int size = ans;
+        for (int i = k; i <= n; i++) {
+            for (int j = k; j <= m; j++) {
+                int tmp = getSum(i, j);
+                int tmpreversed = size - tmp;
+                if (tmp < ans) {
+                    ans = tmp;
+                }
+                if (tmpreversed < ans) {
+                    ans = tmpreversed;
+                }
+            }
+        }
+        System.out.println(ans);
+    }
+    static void setSum(int y, int x) {
+        if (y == 0 && x == 0) {
+            return;
+        }
+        else if (y == 0) {
+            sum[y][x] = sum[y][x-1] + sum[y][x];
+        }
+        else if (x == 0) {
+            sum[y][x] = sum[y-1][x] + sum[y][x];
+        }
+        else {
+            sum[y][x] = sum[y-1][x] + sum[y][x-1] - sum[y-1][x-1] + sum[y][x];
+        }
+    }
+
+    static int getSum(int y, int x) {
+        y-=1;
+        x-=1;
+        int ans = sum[y][x];
+        boolean ydone = false;
+        boolean xdone = false;
+        if (y-k >= 0) {
+            ans -= sum[y - k][x];
+            ydone = true;
+        }
+        if (x-k >= 0) {
+            ans -= sum[y][x-k];
+            xdone = true;
+        }
+        if (ydone && xdone)
+            ans += sum[y-k][x-k];
+        return ans;
+    }
+}