UVa 11549 Open Credit System

题意：给出n个数，找出两个整数a[i],a[j](i < j),使得a[i] - a[j]尽量大

从小到大枚举j,在这个过程中维护a[i]的最大值

maxai晚于ans更新，

可以看这个例子

 1 8 9 10 11

正确的应该是-1

如果更早更新的话，算出来就是0

用数组来存的

 1 #include<iostream>  

 2 #include<cstdio>  

 3 #include<cstring> 

 4 #include <cmath> 

 5 #include<stack>

 6 #include<vector>

 7 #include<map> 

 8 #include<set>

 9 #include<queue> 

10 #include<algorithm>  

11 using namespace std;

12 

13 typedef long long LL;

14 const int INF = (1<<30)-1;

15 const int mod=1000000007;

16 const int maxn=1000005;

17 

18 int a[maxn];

19 int n;

20 

21 int main(){

22     int T;

23     scanf("%d",&T);

24     while(T--){

25         scanf("%d",&n);

26         for(int i = 0;i < n;i++) scanf("%d",&a[i]);

27         int ans = a[0] - a[1];

28         int maxai = a[0];

29         for(int j = 1;j < n;j++){

30             ans = max(ans,maxai - a[j]);

31             maxai = max(maxai,a[j]);

32         //    printf("j = %d  maxai = %d  ans = %d\n",j,maxai,ans);

33         }

34         printf("%d\n",ans);

35     }

36     return 0;

37 }

View Code

边读边算的

 1 #include<iostream>  

 2 #include<cstdio>  

 3 #include<cstring> 

 4 #include <cmath> 

 5 #include<stack>

 6 #include<vector>

 7 #include<map> 

 8 #include<set>

 9 #include<queue> 

10 #include<algorithm>  

11 using namespace std;

12 

13 typedef long long LL;

14 const int INF = (1<<30)-1;

15 const int mod=1000000007;

16 const int maxn=1000005;

17 

18 int main(){

19     int T;

20     scanf("%d",&T);

21     while(T--){

22         int n;

23         scanf("%d",&n);

24 

25         int x,y,ans;

26         scanf("%d %d",&x,&y);

27         ans = x-y;

28         int maxai = x;

29         for(int i = 2;i<n;i++){

30             scanf("%d",&x);

31             ans = max(ans,maxai - x);

32             maxai = max(maxai,x);

33         }

34         printf("%d\n",ans);

35     }

36     return 0;

37 }

View Code