Data-Structures/Array/Max Index

Data-Structures/Array/Max Index

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+<script>
+// For a given array []arr,
+// calculates the maximum j – i
+// such that arr[j] > arr[i]
+
+let v = [34, 8, 10, 3, 2, 80, 30, 33, 1];
+let n = v.length;
+let maxFromEnd = new Array(n + 1);
+
+for (let i = 0; i < maxFromEnd.length; i++)
+maxFromEnd[i] = Number.MIN_VALUE;
+
+// Create an array maxfromEnd
+for (let i = v.length - 1; i >= 0; i--)
+{
+maxFromEnd[i] = Math.max(maxFromEnd[i + 1], v[i]);
+}
+
+let result = 0;
+
+for (let i = 0; i < v.length; i++)
+{
+let low = i + 1, high = v.length - 1, ans = i;
+
+while (low <= high)
+{
+let mid = parseInt((low + high) / 2, 10);
+
+if (v[i] <= maxFromEnd[mid])
+{
+// We store this as current
+// answer and look for further
+// larger number to the right side
+ans = Math.max(ans, mid);
+low = mid + 1;
+}
+else
+{
+high = mid - 1;
+}
+}
+
+// Keeping a track of the
+// maximum difference in indices
+result = Math.max(result, ans - i);
+}
+document.write(result);
+
+</script>