1007 Maximum Subsequence Sum (25分)

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

int main()
{
	int k;
	cin>>k;
	int *arr = new int[k+5];
	int *dp = new int[k+5];
	memset(dp, 0, sizeof(int)*(k+5));
	int flag = 1;
	for(int i=0;i<k;i++){
		cin>>arr[i];
		if(arr[i]>=0)
			flag = 0;
	}
	if(flag)
		cout<<"0"<<" "<<arr[0]<<" "<<arr[k-1]<<endl;
	else{
		dp[0] = arr[0];
		//dp[i]表示以第i个数字结尾的最大和为dp[i]
		for(int i=1;i<k;i++)
			dp[i] = max(dp[i-1]+arr[i], arr[i]);
//		int max_addr = max_element(dp, dp+k) - dp;
		int max_addr=0, maxn = dp[0];
		for(int i=1;i<k;i++)
			if(dp[i] > maxn){
				maxn = dp[i];
				max_addr = i;
			}
		cout<<maxn<<" ";
		int sum=0;
		for(int i=max_addr;i>=0;i--){
			sum += arr[i];
			if(sum == maxn){
				cout<<arr[i]<<" "<<arr[max_addr]<<endl;
				break;
			}
		}
	}
	delete []arr;
	delete []dp;
	return 0;
}

法二：

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

int main()
{
	int k;
	cin>>k;
	int *arr = new int[k+5];
	int *dp = new int[k+5];
	int flag = 1;
	for(int i=0;i<k;i++){
		cin>>arr[i];
		if(arr[i]>=0)
			flag = 0;
	}
	if(flag)
		cout<<"0"<<" "<<arr[0]<<" "<<arr[k-1]<<endl;
	else{
		dp[0] = arr[0];
		int *s = new int[k+5];
		//s[i]=j:存放以dp[i]结尾的开始下标为j 
		//dp[i]表示以第i个数字结尾的最大和为dp[i]
		for(int i=1;i<k;i++){
			if(dp[i-1] + arr[i] > arr[i]){
				dp[i] = dp[i-1] + arr[i];
				s[i] = s[i-1];
			}
			else{
				dp[i] = arr[i];
				s[i] = i;
			}
		}
		int max_addr = max_element(dp, dp+k) - dp;
		cout<<dp[max_addr]<<" "<<arr[s[max_addr]]<<" "<<arr[max_addr]<<endl;
		delete []s;
	}
	delete []arr;
	delete []dp;
	return 0;
}