Create minimum-size-subarray-sum.cpp

Author: kamyu104

C++/minimum-size-subarray-sum.cpp

@@ -0,0 +1,46 @@
+// Time:  O(n)
+// Space: O(1)
+
+// Sliding window solution.
+class Solution {
+public:
+    int minSubArrayLen(int s, vector<int>& nums) {
+        int start = -1, sum = 0, min_size = numeric_limits<int>::max();
+        for (int i = 0; i < nums.size(); ++i) {
+            sum += nums[i];
+            while (sum >= s) {
+                min_size = min(min_size, i - start);
+                sum -= nums[++start];
+            }
+        }
+        if (min_size == numeric_limits<int>::max()) {
+            return 0;
+        }
+        return min_size;
+    }
+};
+
+// Time:  O(nlogn)
+// Space: O(n)
+// Binary search solution.
+class Solution2 {
+public:
+    int minSubArrayLen(int s, vector<int>& nums) {
+        int min_size = numeric_limits<int>::max();
+        vector<int> sum_from_start(nums.size() + 1);
+        partial_sum(nums.cbegin(), nums.cend(), sum_from_start.begin() + 1);
+        for (int i = 0; i < nums.size(); ++i) {
+            const auto& end_it = lower_bound(sum_from_start.cbegin() + i,
+                                             sum_from_start.cend(),
+                                             sum_from_start[i] + s);
+            if (end_it != sum_from_start.cend()) {
+                int end = static_cast<int>(end_it - sum_from_start.cbegin());
+                min_size = min(min_size, end - i);
+            }
+        }
+        if (min_size == numeric_limits<int>::max()) {
+            return 0;
+        }
+        return min_size;
+    }
+};