1104 Sum of Number Segments

本文探讨了C++程序中double*int与int*double操作顺序不同导致的结果差异,并通过两个代码示例展示了这种差异的具体表现。通过对两段代码的对比分析,揭示了数据类型和运算顺序在数值计算中的重要性。

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	#include<iostream>
	using namespace std;
	int main()
	{
		#ifndef ONLINE_JUDGE
		freopen("in.txt","r",stdin);
		#endif
		int n;
		cin>>n;
		double b[100001];
		double ans=0.0;
		for(int i=1;i<=n;i++){
			cin>>b[i];
			ans=ans+i*(n-i+1)*b[i];
		}
		printf("%.2f",ans);
		return 0;
		
	}
#include<iostream>
using namespace std;
int main() {
	#ifndef ONLINE_JUDGE
	freopen("in.txt","r",stdin);
	#endif
    int n;
    cin >> n;
    double a[100001];
    double sum = 0.0;
    for (int i = 1; i <= n; i++) {
        cin >> a[i];
        sum = sum + a[i] * i * (n - i + 1);
    }
    printf("%.2f", sum);
    return 0;
}

double*int和int*double结果不一样!!!第一段15分,第二段代码20分,就是顺序不一样,唉~玄学

Yousef has an array a of size n . He wants to partition the array into one or more contiguous segments such that each element ai belongs to exactly one segment. A partition is called cool if, for every segment bj , all elements in bj also appear in bj+1 (if it exists). That is, every element in a segment must also be present in the segment following it. For example, if a=[1,2,2,3,1,5] , a cool partition Yousef can make is b1=[1,2] , b2=[2,3,1,5] . This is a cool partition because every element in b1 (which are 1 and 2 ) also appears in b2 . In contrast, b1=[1,2,2] , b2=[3,1,5] is not a cool partition, since 2 appears in b1 but not in b2 . Note that after partitioning the array, you do not change the order of the segments. Also, note that if an element appears several times in some segment bj , it only needs to appear at least once in bj+1 . Your task is to help Yousef by finding the maximum number of segments that make a cool partition. Input The first line of the input contains integer t (1≤t≤104 ) — the number of test cases. The first line of each test case contains an integer n (1≤n≤2⋅105 ) — the size of the array. The second line of each test case contains n integers a1,a2,…,an (1≤ai≤n ) — the elements of the array. It is guaranteed that the sum of n over all test cases doesn't exceed 2⋅105 . Output For each test case, print one integer — the maximum number of segments that make a cool partition. Example InputCopy 8 6 1 2 2 3 1 5 8 1 2 1 3 2 1 3 2 5 5 4 3 2 1 10 5 8 7 5 8 5 7 8 10 9 3 1 2 2 9 3 3 1 4 3 2 4 1 2 6 4 5 4 5 6 4 8 1 2 1 2 1 2 1 2 OutputCopy 2 3 1 3 1 3 3 4 Note The first test case is explained in the statement. We can partition it into b1=[1,2] , b2=[2,3,1,5] . It can be shown there is no other partition with more segments. In the second test case, we can partition the array into b1=[1,2] , b2=[1,3,2] , b3=[1,3,2] . The maximum number of segments is 3 . In the third test case, the only partition we can make is b1=[5,4,3,2,1]
最新发布
06-09
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