java: add «1140. Stone Game II»

Signed-off-by: Matej Focko <me@mfocko.xyz>

java/stone-game-ii.java

@@ -0,0 +1,39 @@
+class Solution {
+  private int[] getSuffixSum(int[] piles) {
+    var suffix = new int[piles.length + 1];
+
+    for (int i = piles.length - 1; i >= 0; --i) {
+      suffix[i] = suffix[i + 1] + piles[i];
+    }
+
+    return suffix;
+  }
+
+  private void compute(int n, int[] suffix, int[][] dp, int i) {
+    var row = dp[i];
+
+    for (int maxAllowed = n - 1; maxAllowed >= 1; --maxAllowed) {
+      for (int x = 1; x <= 2 * maxAllowed && i + x <= n; ++x) {
+        row[maxAllowed] = Math.max(row[maxAllowed], suffix[i] - dp[i + x][Math.max(maxAllowed, x)]);
+      }
+    }
+  }
+
+  public int stoneGameII(int[] piles) {
+    int n = piles.length;
+
+    var suffix = getSuffixSum(piles);
+
+    var dp = new int[n + 1][n + 1];
+    // Handle base case.
+    for (int i = 0; i <= n; ++i) {
+      dp[i][n] = suffix[i];
+    }
+
+    for (int i = n - 1; i >= 0; --i) {
+      compute(n, suffix, dp, i);
+    }
+
+    return dp[0][1];
+  }
+}