#feat:leetcode p3548题题解

src/leetcode/p3548/Solution.java

@@ -0,0 +1,108 @@
+package leetcode.p3548;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * @ProjectName: LeetCode
+ * @FileName: Solution
+ * @Author: 杨逸
+ * @Data:2026/3/26 18:07
+ * @Description: https://leetcode.cn/problems/equal-sum-grid-partition-ii/description/
+ * 3548. 等和矩阵分割 II
+ */
+public class Solution {
+    public boolean canPartitionGrid(int[][] grid) {
+        /**
+         * 枚举分界线
+         * 当前值sum大于total/2时,判断能否通过减去一个单元格使的sum=total/2
+         * 使用两个哈希表记录分界线前后的元素
+         * 垂直分割时将矩阵旋转即可
+         * 当只有一列时,只有第一行和最后一行可以减去
+         * 只有一行时,只能减去这行的两端
+         */
+        long total = 0;
+        Map<Long,Integer> suffixMap = new HashMap<>();
+        for (int[] ints : grid) {
+            for (int v : ints) {
+                total += v;
+                Integer count = suffixMap.getOrDefault((long)v, 0);
+                count++;
+                suffixMap.put((long)v,count);
+            }
+        }
+        return check(grid,total, new HashMap<>(suffixMap)) || check(rotate(grid),total,new HashMap<>(suffixMap));
+    }
+
+    private boolean check(int[][] grid, long total, Map<Long, Integer> suffixMap) {
+        Map<Long,Integer> prefixMap = new HashMap<>();
+        long sum = 0;
+        for (int i = 0; i < grid.length-1; i++) {
+            for (int j = 0; j < grid[0].length; j++) {
+                int v = grid[i][j];
+                sum += v;
+                Integer count = prefixMap.getOrDefault((long)v, 0);
+                count++;
+                prefixMap.put((long)v,count);
+                count = suffixMap.get((long)v) - 1;
+                if (count == 0) {
+                    suffixMap.remove((long)v);
+                } else {
+                    suffixMap.put((long)v,count);
+                }
+            }
+
+            if (sum * 2 == total) {
+                //just right
+                return true;
+            }else if (sum * 2 > total) {
+                //subtract prefix
+                long temp = total - sum;
+                long d = sum - temp;
+                if (grid[0].length == 1){
+                    //only one colum
+                    if (grid[0][0] == d || grid[i][0] == d) {
+                        return true;
+                    }
+                }else if(i==0){
+                    //only one line
+                    if (grid[0][0] == d || grid[0][grid[0].length-1] == d) {
+                        return true;
+                    }
+                } else{
+                    if (!prefixMap.getOrDefault(Long.valueOf(d +""),0).equals(0)) {
+                        return true;
+                    }
+                }
+            }else{
+                //subtract suffix
+                long temp = total - sum;
+                long d = temp - sum;
+                if (grid[0].length == 1) {
+                    if (grid[i+1][0] == d || grid[grid.length-1][0] == d) {
+                        return true;
+                    }
+                }else if(i==grid.length-2){
+                    if (grid[i+1][0] == d || grid[i+1][grid[0].length-1] == d) {
+                        return true;
+                    }
+                } else{
+                    if (!suffixMap.getOrDefault(Long.valueOf(d +""),0).equals(0)) {
+                        return true;
+                    }
+                }
+            }
+        }
+        return false;
+    }
+    private int[][] rotate(int[][] grid) {
+        int m = grid.length, n = grid[0].length;
+        int[][] result = new int[n][m];
+        for (int i = 0; i < m; i++) {
+            for (int j = 0; j < n; j++) {
+                result[j][m - 1 - i] = grid[i][j];
+            }
+        }
+        return result;
+    }
+}

src/leetcode/p3548/SolutionTest.java

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+package leetcode.p3548;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+
+import java.util.Arrays;
+import java.util.Collection;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * @ProjectName: LeetCode
+ * @FileName: SolutionTest
+ * @Author: 杨逸
+ * @Data:2026/3/26 18:49
+ * @Description:
+ */
+@RunWith(Parameterized.class)
+public class SolutionTest {
+    public static final Solution solution = new Solution();
+    private final int[][] grid;
+    private final boolean expected;
+
+    public SolutionTest(int[][] grid, boolean expected) {
+        this.grid = grid;
+        this.expected = expected;
+    }
+    @Parameterized.Parameters
+    public static Collection<Object[]> data() {
+        return Arrays.asList(new Object[][]{
+                {new int[][]{{1,4},{2,3}},true},
+                {new int[][]{{1,2},{3,4}},true},
+                {new int[][]{{1,2,4},{2,3,5}},false},
+                {new int[][]{{4,1,8},{3,2,6}},false},
+        });
+    }
+
+    @Test(timeout = 1000L)
+    public void canPartitionGrid() {
+        assertEquals(expected,solution.canPartitionGrid(grid));
+    }
+}