Non Decreasing 😐

Author: Hazrat-Ali9

non-decreasing-array.js

@@ -0,0 +1,41 @@
+/**
+ * @param {number[]} nums
+ * @return {boolean}
+ */
+const checkPossibility = nums => {
+  let p = null;
+
+  for (let i = 0; i < nums.length - 1; i++) {
+    if (nums[i] > nums[i + 1]) {
+      if (p !== null) {
+        return false;
+      }
+      p = i;
+    }
+  }
+
+  // array is sorted already
+  if (p === null) {
+    return true;
+  }
+
+  // only the first and last pair need to be fixed
+  if (p === 0 || p === nums.length - 2) {
+    return true;
+  }
+
+  // considering A[p-1], A[p], A[p+1], A[p+2]
+  // e.g. 2, 4, 3, 5
+  if (nums[p - 1] <= nums[p + 1]) {
+    return true;
+  }
+
+  // e.g 5, 5, 4, 6
+  if (nums[p] <= nums[p + 2]) {
+    return true;
+  }
+
+  return false;
+};
+
+export { checkPossibility };