1011. Capacity To Ship Packages Within D Days

1011/1011.md

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+## 何も見ずに解いてみる
+
+```cpp
+class Solution {
+public:
+    int shipWithinDays(vector<int>& weights, int days) {
+        int capacity_min = *max_element(weights.begin(), weights.end());
+        int capacity_max = accumulate(weights.begin(), weights.end(), 0);
+        while (capacity_min < capacity_max) {
+            int capacity_mid = capacity_min + (capacity_max - capacity_min) / 2;
+            if (can_ship(weights, days, capacity_mid)) {
+                capacity_max = capacity_mid;
+            }
+            else {
+                capacity_min = capacity_mid + 1;
+            }
+        }
+        return capacity_min;
+    }
+private:
+    bool can_ship(vector<int>& weights, int days, int capacity) {
+        int current_day = 1;
+        int load = 0;
+        for (int weight : weights) {
+            if (load + weight <= capacity) {
+                load += weight;
+            }
+            else {
+                if (weight > capacity) {
+                    return false;
+                }
+                current_day += 1;
+                if (current_day > days) {
+                    return false;
+                }
+                load = weight;
+            }
+        }
+        return true;
+    }
+};
+```
+
+## 他の人のコードを見てみる
+
+https://github.com/tokuhirat/LeetCode/pull/44/files  
+https://github.com/ryosuketc/leetcode_arai60/pull/33/files  
+https://github.com/Ryotaro25/leetcode_first60/pull/51/files  
+https://github.com/goto-untrapped/Arai60/pull/41/files  
+
+## 最終コード
+
+weightsとdaysをキャプチャしたいと思ったのでラムダ式で書いてみました。
+
+```cpp
+if (++current_day > days) {
+// ...
+}
+```
+の部分は
+```cpp
+++current_day;
+if (current_day > days) {
+// ...
+}
+```
+の方が一般的なんですかね？調べた感じどっちも結構ありそうでした。
+
+```cpp
+class Solution {
+public:
+    int shipWithinDays(vector<int>& weights, int days) {
+        auto can_ship = [&weights, days](int capacity) -> bool {
+            int current_day = 1;
+            int load = 0;
+            for (int weight : weights) {
+                if (load + weight <= capacity) {
+                    load += weight;
+                }
+                else {
+                    if (weight > capacity) {
+                        return false;
+                    }
+                    if (++current_day > days) {
+                        return false;
+                    }
+                    load = weight;
+                }
+            }
+            return true;
+        };
+        int low = *max_element(weights.begin(), weights.end());
+        int high = accumulate(weights.begin(), weights.end(), 0);
+        while (low < high) {
+            int mid = low + (high - low) / 2;
+            if (can_ship(mid)) {
+                high = mid;
+            }
+            else {
+                low = mid + 1;
+            }
+        }
+        return low;
+    }
+};
+```
+
+`current_day`を`0`で初期化してしまい一敗・・・  
+`1`から始める方が現実世界の考え方には即しているような気がするのでこのままにします