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01-复杂度2 Maximum Subsequence Sum

2021-08-11  本文已影响0人  你的鱼干

本题本质上是一个简单的最大子列问题


Question

Given a sequence of K integers { N1, N 2, ..., NK}. A continuous subsequence is defined to be { Ni , Ni+1, ..., Nj} where 1≤i≤j≤K. The Maximum Subsequence is the continuous subsequence which has the largest sum of its elements. For example, given sequence { -2, 11, -4, 13, -5, -2 }, its maximum subsequence is { 11, -4, 13 } with the largest sum being 20.
Now you are supposed to find the largest sum, together with the first and the last numbers of the maximum subsequence

Input Specification:

Each input file contains one test case. Each case occupies two lines. The first line contains a positive integer K (≤10000). The second line contains K numbers, separated by a space.

Output Specification:

For each test case, output in one line the largest sum, together with the first and the last numbers of the maximum subsequence. The numbers must be separated by one space, but there must be no extra space at the end of a line. In case that the maximum subsequence is not unique, output the one with the smallest indices i and j (as shown by the sample case). If all the K numbers are negative, then its maximum sum is defined to be 0, and you are supposed to output the first and the last numbers of the whole sequence.

Sample Input:

10
-10 1 2 3 4 -5 -23 3 7 -21

Sample Output:

10 1 4

My Code

#include<stdio.h>

int main()
{
    int k,i,n1=0,n2=0,count;
    int thisSum=0,maxSum=0,startNum,endNum;
    scanf(
        "%d", &k);
    int List[k];
    for(i=0; i<k; i++)
        scanf("%d", &List[i]);
    for(i=0; i<k; i++)
    {
        thisSum += List[i];
        n2 = i;
        if(thisSum > maxSum)
        {
            maxSum = thisSum;
            startNum = List[n1];
            endNum = List[n2];
        }
        else if(thisSum < 0)
        {
            thisSum = 0;
            if(i<k-1)
                n1 = i+1;
        }
    }
    for(i=0; i<k; i++)
    {
        if(List[i]>=0)
            count += 1;
    }
    if(count == 0)
    {
        startNum = List[0];
        endNum = List[k-1];
    }
    printf("%d %d %d", maxSum, startNum, endNum);
    return 0;
}

Outcome

Outcome

本文采用的方法是在线处理
The\ method\ used\ in\ this\ paper\ is\ online\ processing

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