POJ2479 - Maximum sum （动规）

题目链接 : poj2479 - Maximum sum

思路

最大连续子列和

for(int i=2; i=n; i++) f(i) = max( f(i), f(i-2) );

代码

#include <iostream>
#include <cstdio>
#include <algorithm>
const int inf = 0x7ffffff;

using namespace std;
int num[50010], s[50010], e[50010];

int main()
{
int t, n, maxsum, sum;
scanf("%d", &t);
while(t--)
{
scanf("%d", &n);
for(int i=1; i<=n; i++) scanf("%d", num+i);

s[1] = num[1];
for(int i=2; i<=n; i++)
{
if(s[i-1]>0) s[i] = s[i-1] + num[i];
else s[i] = num[i];
}
for(int i=2; i<=n; i++) s[i] = max(s[i], s[i-1]);

e
= num
;
for(int i=n-1; i>=1; i--)
{
if(e[i+1]>0) e[i] = e[i+1] + num[i];
else e[i] = num[i];
}
for(int i=n-1; i>=1; i--) e[i] = max(e[i+1], e[i]);

maxsum = -inf;
for(int i=1; i<n; i++)
{
sum = s[i] + e[i+1];
if(sum>maxsum) maxsum = sum;
}

printf("%d\n", maxsum);
}
}