Create a0931 Minimum falling path sum

src/main/java/problemset/a0931/MinFallingPathSum.java

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+package problemset.a0931;
+
+public class MinFallingPathSum {
+    public int minFallingPathSum(int[][] matrix) {
+        int n = matrix.length;
+        var f = new int[n];
+        for (var row : matrix) {
+            var g = f.clone();
+            for (int j = 0; j < n; j++) {
+                if (j > 0) g[j] = Math.min(g[j], f[j - 1]);
+                if (j + 1 < n) g[j] = Math.min(g[j], g[j + 1]);
+                g[j] += row[j];
+            }
+            f = g;
+        }
+        int ans = Integer.MAX_VALUE;
+        for (var x : f)
+            ans = Math.min(ans, x);
+        return ans;
+    }
+}

src/test/java/problemset/a0931/MinFallingPathSumTest.java

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+package problemset.a0931;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class MinFallingPathSumTest {
+
+    private MinFallingPathSum sum;
+    private int[][] testcaseOne;
+    private int[][] testcaseTwo;
+
+    @BeforeEach
+    void setUp() {
+        sum = new MinFallingPathSum();
+        testcaseOne = new int[][]{{2, 1, 3}, {6, 5, 4}, {7, 8, 9}};
+        testcaseTwo = new int[][]{{-19, 57}, {-40, -5}};
+    }
+
+    @Test
+    void test_minFallingPathSum_v1() {
+        var expectedResult = 13;
+        var actualResult = sum.minFallingPathSum(testcaseOne);
+        assertEquals(expectedResult, actualResult);
+    }
+
+    @Test
+    void test_minFallingPathSum_v2() {
+        var expectedResult = -59;
+        var actualResult = sum.minFallingPathSum(testcaseTwo);
+        assertEquals(expectedResult, actualResult);
+    }
+}