From e4de63f774cf7eda0172b36eafddbb76db889b4a Mon Sep 17 00:00:00 2001
From: Animax Deng <animax.deng@gmail.com>
Date: Sat, 28 Dec 2019 00:43:05 -0600
Subject: [PATCH] Add solution for Capacity To Ship Packages Within D days

---
 .../CapacityToShipPackagesWithinDdays.swift   | 45 +++++++++++++++++++
 1 file changed, 45 insertions(+)
 create mode 100644 Search/CapacityToShipPackagesWithinDdays.swift

diff --git a/Search/CapacityToShipPackagesWithinDdays.swift b/Search/CapacityToShipPackagesWithinDdays.swift
new file mode 100644
index 00000000..049f5712
--- /dev/null
+++ b/Search/CapacityToShipPackagesWithinDdays.swift
@@ -0,0 +1,45 @@
+/**
+ * Question Link: https://leetcode.com/problems/capacity-to-ship-packages-within-d-days/
+ * Primary idea: Binary Search, minimum possible value is max number in weights; 
+ *               maximum possible value is the sum of weights. canShip function simulate if all item can be ship.
+ *
+ * Time Complexity: O(Wlogn), Space Complexity: O(1)
+ */
+
+class Solution {
+    func shipWithinDays(_ weights: [Int], _ D: Int) -> Int {
+        if weights.count <= 0 {
+            return 0
+        }
+        
+        var l = weights.max()!, r = weights.reduce(0) { $0 + $1 }
+        
+        while l <= r {
+            let mid = Int((r - l) / 2 + l)
+            if canShip(weights, D, mid) {
+                r = mid - 1
+            } else {
+                l = mid + 1
+            }
+        }
+        
+        return l
+    }
+    func canShip(_ weights: [Int], _ D: Int, _ cap:Int) -> Bool {
+        var visited = Set<Int>()
+        
+        var rest = cap, day = 0
+        for (idx, w) in weights.enumerated() {
+            if rest - w < 0 {
+                day += 1
+                if day >= D {
+                    return false
+                }
+                rest = cap
+            }
+            rest -= w
+        }
+        
+        return true
+    }
+}