【 USACO11JAN】 利潤 【洛谷P3009】

P3009 [USACO11JAN]利潤Profits

題目描述

The cows have opened a new business, and Farmer John wants to see how well they are doing. The business has been running for N (1 <= N <= 100,000) days, and every day i the cows recorded their net profit P_i (-1,000 <= P_i <= 1,000).

Farmer John wants to find the largest total profit that the cows have made during any consecutive time period. (Note that a consecutive time period can range in length from one day through N days.) Help him by writing a program to calculate the largest sum of consecutive profits.

牛們開了家新公司，這家公司已經運作了N天，財務報表顯示第i天獲得的利潤爲Pi ， 有些天的利潤可能是個負數。約翰想給奶牛公司寫個新聞報道，以吹噓她們的業績。於是他 想知道，這家公司在哪一段連續的日子裏，利潤總和是最大的。

輸入輸出格式

輸入格式：

• Line 1: A single integer: N

• Lines 2..N+1: Line i+1 contains a single integer: P_i

輸出格式：

• Line 1: A single integer representing the value of the maximum sum of profits for any consecutive time period.

輸入輸出樣例

輸入樣例#1：

7 
-3 
4 
9 
-2 
-5 
8 
-3 

輸出樣例#1：

14 

說明

The maximum sum is obtained by taking the sum from the second through the sixth number (4, 9, -2, -5, 8) => 14.

這道題很裸，但是思想和方法非常重要，儘管比較簡單。

不給詳細解釋，請大家仔細研讀代碼，如有不明，私信或評論或Q我（568251782）均可

#include<iostream>
#include<cstdio>
#include<cstring>
#include<cstdlib>

const int MAXN  = 100000 + 10;
const int INF = 99999999;

int n,ans;
int num[MAXN];


int main()
{
	scanf("%d", &n);
	ans = -1*INF;
	for(int i= 1;i <= n;i++)
	{
		scanf("%d", &num[i]);
		if(num[i-1] > 0)
		{
			num[i] += num[i-1];
		}
		ans = std::max(ans, num[i]);
	}
	printf("%d", ans);
	return 0;
}