8ms, 95%, 60%. binary search.

Author: Jeromestein

1011.capacity-to-ship-packages-within-d-days.java

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+/*
+ * @lc app=leetcode id=1011 lang=java
+ *
+ * [1011] Capacity To Ship Packages Within D Days
+ */
+
+// @lc code=start
+
+/**
+ * Explanation
+ * Given the number of bags,
+ * return the minimum capacity of each bag,
+ * so that we can put items one by one into all bags.
+ * 
+ * We binary search the final result.
+ * The left bound is max(A), The right bound is sum(A).
+ */
+class Solution {
+    public int shipWithinDays(int[] weights, int D) {
+        int left = 0, right = 0;
+        for (int w : weights) {
+            left = Math.max(left, w);
+            right += w;
+        }
+        while (left < right) {
+            int mid = (left + right) / 2;
+            if (getNeed(weights, mid) > D)
+                left = mid + 1;
+            else
+                right = mid;
+        }
+        return left;
+    }
+
+    public int getNeed(int[] weights, int mid) {
+        int need = 1, cur = 0;
+        for (int w : weights) {
+            if (cur + w > mid) {
+                need += 1;
+                cur = 0;
+            }
+            cur += w;
+        }
+
+        return need;
+    }
+}
+// @lc code=end