Problem Description
Given a sequence a[1],a[2],a[3]…a[n], your job is to calculate the max sum of a sub-sequence. For example, given (6,-1,5,4,-7), the max sum in this sequence is 6 + (-1) + 5 + 4 = 14.
Input
The first line of the input contains an integer T(1<=T<=20) which means the number of test cases. Then T lines follow, each line starts with a number N(1<=N<=100000), then N integers followed(all the integers are between -1000 and 1000).
Output
For each test case, you should output two lines. The first line is “Case #:”, # means the number of the test case. The second line contains three integers, the Max Sum in the sequence, the start position of the sub-sequence, the end position of the sub-sequence. If there are more than one result, output the first one. Output a blank line between two cases
Sample Input
2
5 6 -1 5 4 -7
7 0 6 -1 1 -6 7 -5
Sample Output
Case 1:
14 1 4
Case 2:
7 1 6
本题为动态规划问题,求最大连续子区间和,并且输出和,起始位置,结束位置
思路:输入一组数据,用summax来跟踪最大和,sum做连加运算的跟踪,k来跟踪最大区间的起始位置
当sum<0时,置sum=0(因为当前的连加和为负的话,若后面继续为负责越加越小,若后面为正,那么从后面作为sum的起始更合适),并且让k移动到后一位,即k=i+2(因为k从1初始,i从0初始,k向后移动一位相当于i+2,)
#include <iostream>
#include <cstdio>
using namespace std;
int main(){
int t,n,c,i;
int a[100002];
scanf("%d\n",&t);
for(c=0;c<t;c++){
int summax=-1000,sum=0,st=0,en=0,k=1;
scanf("%d",&n);
for(i=0;i<n;i++){
scanf("%d",&a[i]);
}
for(i=0;i<n;i++){
sum+=a[i];
if(summax<sum){
summax=sum;
st=k;
en=i+1;
}
if(sum<0){
sum=0;
k=i+2;
}
}
printf("case %d:\n%d %d %d\n",c,summax,st,en);
if(c!=t)cout<<endl;
}
return 0;
}