209. Minimum Size Subarray Sum

209/209.md

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+## 何も見ずに解いてみる
+
+```cpp
+class Solution {
+public:
+    int minSubArrayLen(int target, vector<int>& nums) {
+        int start = 0;
+        int sum = 0;
+        int min_length = INT_MAX;
+        for (int end = 0; end < nums.size(); ++end) {
+            sum += nums[end];
+            while (sum - nums[start] >= target) {
+                sum -= nums[start];
+                ++start;
+            }
+            if (sum >= target) {
+                min_length = min(min_length, end - start + 1);
+            }
+        }
+        if (min_length == INT_MAX) {
+            return 0;
+        }
+        return min_length;
+    }
+};
+```
+
+## 他の人のコードを見てみる
+
+https://github.com/tokuhirat/LeetCode/pull/49/files  
+https://github.com/hayashi-ay/leetcode/pull/51/files  
+https://github.com/Fuminiton/LeetCode/pull/51/files  
+https://github.com/Ryotaro25/leetcode_first60/pull/53/files  
+
+INT_MAXよリモstd::numeric_limits<int>::max()の方が安全らしいが書くのが面倒・・・
+
+試しにwhile文とインクリメントを使って書いてみる。あんまり読みやすくはないかも。
+
+```cpp
+class Solution {
+public:
+    int minSubArrayLen(int target, vector<int>& nums) {
+        int start = 0;
+        int end = 0;
+        int sum = 0;
+        int min_length = std::numeric_limits<int>::max();
+        while (end < nums.size()) {
+            while (sum < target && end < nums.size()) {
+                sum += nums[end++];
+            }
+            while (sum >= target) {
+                min_length = min(min_length, end - start);
+                sum -= nums[start++];
+            }
+        }
+        if (min_length == std::numeric_limits<int>::max()) {
+            return 0;
+        }
+        return min_length;
+    }
+};
+```
+
+## 最終コード
+
+```cpp
+class Solution {
+public:
+    int minSubArrayLen(int target, vector<int>& nums) {
+        int min_length = std::numeric_limits<int>::max();
+        int start = 0;
+        int sum = 0;
+        for (int end = 0; end < nums.size(); ++end) {
+            sum += nums[end];
+            while (sum >= target) {
+                min_length = min(min_length, end - start + 1);
+                sum -= nums[start];
+                ++start;
+            }
+        }
+        if (min_length == std::numeric_limits<int>::max()) {
+            return 0;
+        }
+        return min_length;
+    }
+};
+```
+