Ehab loves number theory, but for some reason he hates the number x. Given an array a, find the length of its longest subarray such that the sum of its elements isn’t divisible by x, or determine that such subarray doesn’t exist.

An array a is a subarray of an array b if a can be obtained from b by deletion of several (possibly, zero or all) elements from the beginning and several (possibly, zero or all) elements from the end.

Input
The first line contains an integer t (1≤t≤5) — the number of test cases you need to solve. The description of the test cases follows.

The first line of each test case contains 2 integers n and x (1≤n≤105, 1≤x≤104) — the number of elements in the array a and the number that Ehab hates.

The second line contains n space-separated integers a1, a2, …, an (0≤ai≤104) — the elements of the array a.

Output
For each testcase, print the length of the longest subarray whose sum isn’t divisible by x. If there’s no such subarray, print ?1.

Example
Input
3
3 3
1 2 3
3 4
1 2 3
2 2
0 6
Output
2
3
-1
Note
In the first test case, the subarray [2,3] has sum of elements 5, which isn’t divisible by 3.

In the second test case, the sum of elements of the whole array is 6, which isn’t divisible by 4.

In the third test case, all subarrays have an even sum, so the answer is ?1.

思路：一開始想復雜了，我們比較一下從左邊刪除數字和從右邊刪除數字，最終剩下的長度，選取最大的那個就行了。
代碼如下：

#include<bits/stdc++.h> #define ll long long using namespace std;const int maxx=1e5+100; int a[maxx]; int sum[maxx]; int n,x;int main() {int t;scanf("%d",&t);while(t--){scanf("%d%d",&n,&x);memset(sum,0,sizeof(sum));for(int i=1;i<=n;i++) scanf("%d",&a[i]),sum[i]=sum[i-1]+a[i];if(sum[n]%x) cout<<n<<endl;else{int ans=-1;for(int i=1;i<=n;i++){if((sum[n]-sum[i])%x){ans=max(ans,n-i);break;}}for(int i=n;i>=1;i--){if(sum[i]%x){ans=max(ans,i);break;}}cout<<ans<<endl;}}return 0; }

努力加油a啊，(^o)/~

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