Solve Problem 862 - Shortest Subarray with Sum at Least K

Author: Hieu Luong

src/monotone/Problem862_ShortestSubarrayWithSumAtLeastK.java

@@ -0,0 +1,27 @@
+package monotone;
+
+import java.util.Deque;
+import java.util.LinkedList;
+
+public class Problem862_ShortestSubarrayWithSumAtLeastK {
+
+    public int shortestSubarray(int[] A, int K) {
+        // B[j] - B[i] >= K ---> find smallest (j-i);
+        Deque<Integer> deque = new LinkedList<>();
+        int n = A.length, res = n+1, B[] = new int[n+1];
+
+        for (int i = 0; i < n; i++) B[i+1] += B[i] + A[i];
+
+        for (int i = 0; i < n+1; i++) {
+            while (!deque.isEmpty() && B[i] - B[deque.peekFirst()] >= K) {
+                res = Math.min(res, i-deque.pollFirst());
+            }
+            while (!deque.isEmpty() && B[i] <= B[deque.peekLast()]) {
+                deque.pollLast();
+            }
+            deque.addLast(i);
+        }
+
+        return res == n+1 ? -1 : res;
+    }
+}