Data Structure Array: Given an array arr[], find the maximum j – i such that arr[j] > arr[i]

http://www.geeksforgeeks.org/given-an-array-arr-find-the-maximum-j-i-such-that-arrj-arri/

 1 #include <iostream>

 2 #include <vector>

 3 #include <algorithm>

 4 #include <queue>

 5 #include <stack>

 6 #include <string>

 7 #include <fstream>

 8 #include <map>

 9 using namespace std;

10 

11 int maxindexdiff(int arr[], int n) {

12     vector<int> L(n), R(n);

13     L[0] = arr[0];

14     for (int i = 1; i < n; i++) L[i] = min(L[i-1], arr[i]);

15     R[n-1] = arr[n-1];

16     for (int i = n-2; i >= 0; i--) R[i] = max(R[i+1], arr[i]);

17     int left, right, ans;

18     left = right = 0;

19     ans = -1;

20     while (left < n && right < n) {

21         if (L[left] < R[right]) {

22             ans = max(ans, right - left);

23             right++;

24         }

25         else left++;

26     }

27     return ans;

28 }

29 

30 int main() {

31     int arr[10] = {9, 2, 3, 4, 5, 6, 7, 8, 18, 0};

32     cout << maxindexdiff(arr, 10) << endl;

33     return 0;

34 }