Implement filling-bookcase-shelves

name: filling-bookcase-shelves
url: https://leetcode.com/problems/filling-bookcase-shelves
difficulty: 2

time: 4 ms
time-rank: 99.17 %
time-complexity: O(N^2)

space: 8.2 MB
space-rank: 95.22 %
space-complexity: O(N)

Fixes #167

Signed-off-by: Christopher Friedt <[email protected]>

Author: cfriedt

filling-bookcase-shelves-test.cpp

@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) 2021, Christopher Friedt
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#include <gtest/gtest.h>
+
+#include "filling-bookcase-shelves.cpp"
+
+using namespace std;
+
+TEST(FillingBookcaseShelves, 1_1_2_3_2_3_1_1_1_1_1_1_1_2__4) {
+  vector<vector<int>> books = {{1, 1}, {2, 3}, {2, 3}, {1, 1},
+                               {1, 1}, {1, 1}, {1, 2}};
+  int shelf_width = 4;
+  int expected = 6;
+  EXPECT_EQ(expected, Solution().minHeightShelves(books, shelf_width));
+}
+
+TEST(FillingBookcaseShelves, 1_3_2_4_3_2__6) {
+  vector<vector<int>> books = {{1, 3}, {2, 4}, {3, 2}};
+  int shelf_width = 6;
+  int expected = 4;
+  EXPECT_EQ(expected, Solution().minHeightShelves(books, shelf_width));
+}
+
+TEST(FillingBookcaseShelves, 7_3_8_7_2_7_2_5__10) {
+  vector<vector<int>> books = {{7,3},{8,7},{2,7},{2,5}};
+  int shelf_width = 10;
+  int expected = 15;
+  EXPECT_EQ(expected, Solution().minHeightShelves(books, shelf_width));
+}

filling-bookcase-shelves.cpp

@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2021, Christopher Friedt
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+// clang-format off
+// name: filling-bookcase-shelves
+// url: https://leetcode.com/problems/filling-bookcase-shelves
+// difficulty: 2
+// clang-format on
+
+#include <climits>
+#include <vector>
+
+using namespace std;
+
+class Solution {
+public:
+
+  int minHeightShelves(vector<vector<int>> &books, int shelf_width) {
+    const size_t N = books.size();
+    auto dp = vector<int>(N + 1, INT_MAX);
+    dp[0] = 0;
+    for(size_t i = 0; i < N; ++i) {
+      for(int j = i, width = 0, height = 0; j >= 0; --j) {
+        width += books[j][0];
+        if (width > shelf_width) {
+          break;
+        }
+        height = max(height, books[j][1]);
+        dp[i + 1] = min(dp[i + 1], dp[j] + height);
+      }
+    }
+
+    return dp[N];
+  }
+};