uva11078 - Open Credit System（动态维护关键值）

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<string>
#include<cmath>
#include<map>
#include<set>
#include<vector>
#include<list>
#include<deque>
#include<algorithm>
#include<stack>
#include<queue>
#include<cctype>
#include<sstream>
using namespace std;
#define pii pair<int,int>
typedef long long int LL;
const double eps=1e-10;
const int INF=1000000000;
const int maxn=100000+10;
int T,n,A[maxn];
int main()
{
    //freopen("in1.txt","r",stdin);
    //freopen("out.txt","w",stdout);
    scanf("%d",&T);
    while(T--)
    {
        //cout<<"#"<<endl;
        scanf("%d",&n);
        for(int i=0;i<n;i++)
        {
            scanf("%d",&A[i]);
        }
        int ans=A[0]-A[1];
        int maxai=A[0];
        for(int i=1;i<n;i++)
        {
            //cout<<maxai<<"&"<<ans<<endl;
            ans=max(ans,maxai-A[i]);
            maxai=max(maxai,A[i]);
        }
        printf("%d\n",ans);
    }
    return 0;
}