Add solution for Maximum Number of Points with Cost

Author: jihyun-um

README.md

@@ -131,4 +131,5 @@ Algorithm exercises from LeetCode implemented in Java (v11) and JavaScript.
 ### Dynamic Programming
 - Count Sorted Vowel Strings | [Problem](https://leetcode.com/problems/count-sorted-vowel-strings) | [Java Solution](src/javacode/solutions/CountSortedVowelStrings.java)
 - Count Square Submatrices with All Ones | [Problem](https://leetcode.com/problems/count-square-submatrices-with-all-ones) | [Java Solution](src/javacode/solutions/CountSquareSubmatrices.java)
-- Minimum Falling Path Sum | [Problem](https://leetcode.com/problems/minimum-falling-path-sum) | [Java Solution](src/javacode/solutions/MinimumFallingPathSum.java)
+- Minimum Falling Path Sum | [Problem](https://leetcode.com/problems/minimum-falling-path-sum) | [Java Solution](src/javacode/solutions/MinimumFallingPathSum.java)
+- Maximum Number of Points with Cost | [Problem](https://leetcode.com/problems/maximum-number-of-points-with-cost) | [Java Solution](src/javacode/solutions/MaximumNumberOfPointsWithCost.java)

src/javacode/solutions/MaximumNumberOfPointsWithCost.java

@@ -0,0 +1,50 @@
+package javacode.solutions;
+
+// [Problem] https://leetcode.com/problems/maximum-number-of-points-with-cost
+class MaximumNumberOfPointsWithCost {
+    // Dynamic programming
+    // O(m * n) time, O(n) space
+    // where m = row size, n = column size
+    public long maxPoints(int[][] points) {
+        int rowSize = points.length, colSize = points[0].length;
+        long[] prevRow = new long[colSize];
+        for (int col = 0; col < colSize; col++) {
+            prevRow[col] = points[0][col];
+        }
+        for (int row = 1; row < rowSize; row++) {
+            long[] left = new long[colSize], right = new long[colSize], currentRow = new long[colSize];
+            left[0] = prevRow[0];
+            for (int i = 1; i < colSize; i++) {
+                left[i] = Math.max(left[i - 1] - 1, prevRow[i]);
+            }
+            right[colSize - 1] = prevRow[colSize - 1];
+            for (int j = colSize - 2; j >= 0; j--) {
+                right[j] = Math.max(right[j + 1] - 1, prevRow[j]);
+            }
+            for (int k = 0; k < colSize; k++) {
+                currentRow[k] = Math.max(left[k], right[k]) + points[row][k];
+            }
+            prevRow = currentRow;
+        }
+        long max = 0;
+        for (int i = 0; i < colSize; i++) {
+            max = Math.max(prevRow[i], max);
+        }
+        return max;
+    }
+
+    // Test
+    public static void main(String[] args) {
+        MaximumNumberOfPointsWithCost solution = new MaximumNumberOfPointsWithCost();
+
+        int[][] input = {
+                {1, 2, 3},
+                {1, 5, 1},
+                {3, 1, 1}
+        };
+        long expectedOutput = 9;
+        long actualOutput = solution.maxPoints(input);
+
+        System.out.println("Test passed? " + (expectedOutput == actualOutput));
+    }
+}