can anyone explain me why my reccurence relation is wrong ??

question : https://www.hackerrank.com/challenges/sherlock-and-cost/problem

my code : https://www.hackerrank.com/challenges/sherlock-and-cost/submissions/code/67767333

I have not memoized it ! Im getting wrong answer for some test cases !

I dont see any WA,they are tle’s.And yeah ur code is not visible.

yeah they are TLE’s but when i check for some cases im getting slight variation in my answer !

ideone : https://ideone.com/U3jKFb

anyone pls help me !

Your code is not readable in current state. Please format it better.

since a[i]>=1 you already know what max and min will return. no need to make 120+ char line code.

What does the return value of f(i, sum) represents?

Also why do you use long long for everything?

My code:

```
#include <bits/stdc++.h>
using namespace std;
const int N = 1e5;
int dp[N][2]; // dp[i][j] => max cost of a[1..i] with a[i] = jth element of {1, b[i]}
int cost(vector <int> b) {
int n = b.size();
for(int i=1;i<n;i++) {
dp[i][0] = max(dp[i-1][0], dp[i-1][1] + abs(1-b[i-1]));
dp[i][1] = max(dp[i-1][0] + abs(b[i]-1), dp[i-1][1] + abs(b[i]-b[i-1]));
}
return max(dp[n-1][0], dp[n-1][1]);
}
int main() {
int t;
cin >> t;
for(int a0 = 0; a0 < t; a0++){
int n;
cin >> n;
vector<int> arr(n);
for(int arr_i = 0; arr_i < n; arr_i++){
cin >> arr[arr_i];
}
int result = cost(arr);
cout << result << endl;
}
return 0;
}
```

Thank you for ur help bro !

But can you explain me where Im going wrong ? Iam checking all four possiblities i.e,(min,min),(min,max),(max,min),(max,max) for current and next element and picking up the maximum sum among them !

ok so you are using sum as an accumulator then?

Here is why your approach is wrong: you set the value of (a[i], a[i+1]) so as to maximize the answer greedily then you again modify the value of (a[i+1], a[i+2]). So basically you may use 2 values at the same time for a[i+1]

oh got it !

Thanks bro !