hdoj 5586 Sum (最大连续子段和)

转变一下思维， 求差值最大连续字段和, 因为最后结果只增不减;

#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;

#define N 100000+100
typedef long long LL;

const LL INF = 0x3f3f3f3f;
LL num[N], transNum[N], dp[N];

inline LL f(LL a){
    return (1890* a +143)% 10007;    
}
int main()
{
    int n;
    while(scanf("%d", &n) != EOF)
    {
        LL sum=0;
        for(int i=1; i<= n; i++)
        {
            scanf("%lld", &num[i]);
            sum+= num[i];
        }
        for(int i=1; i<= n; i++)
        {
            transNum[i]= f(num[i])-num[i];
        }
        memset(dp, 0, sizeof(dp));
        LL maxsum =0;
        for(int i=1; i<= n; i++)
        {
            dp[i]= dp[i-1]>0? dp[i]+dp[i-1]+transNum[i]: dp[i]+transNum[i];
            maxsum =max(maxsum, dp[i]);
        }
        printf("%lld
", maxsum+ sum);
    }
    return 0; 
}