C++ 解法, 执行用时: 7ms, 内存消耗: 420KB, 提交时间: 2022-08-05

#include<cstdio>
#include<algorithm>

using namespace std;

template <typename T>
inline void read(T& f) {
	f = 0;
	T fu = 1;
	char c = getchar();
	while (c < '0' || c > '9') {
		if (c == '-') {
			fu = -1;
		}
		c = getchar();
	}
	while (c >= '0' && c <= '9') {
		f = (f << 3) + (f << 1) + (c & 15);
		c = getchar();
	}
	f *= fu;
}
template <typename T>
inline void print(T x) {
	if (x < 0) putchar('-'), x = -x;
	if (x < 10) putchar(x + 48);
	else print(x / 10), putchar(x % 10 + 48);
}

int main(){
    int maxs;                //结果
    int dpmax, dpmin;        //以i位结尾的子数组最大的乘积,以i位结尾的子数组最小的乘积
    int nmax, nmin;    //新最大最小值
    int num;
    int n;
    
    read(n);
    read(num);
    dpmax = dpmin = maxs = num;
    for(int i = 1;i < n;i++){
        read(num);
        if(num < 0)
            nmax = max(dpmin * num, num);
        else
            nmax = max(dpmax * num, num);
        nmin = min(num, min(dpmin * num, dpmax * num));
        dpmax = nmax, dpmin = nmin;
        maxs = max(dpmax, maxs);
    }
    print(maxs);
    
    return 0;
}

C++ 解法, 执行用时: 10ms, 内存消耗: 2700KB, 提交时间: 2022-03-11

#include <bits/stdc++.h>
using namespace std;
template <typename T>
inline void read(T &f)
{
    f=0;T fu=1;char c=getchar();
    while(c<'0'||c>'9') {if(c=='-'){fu=-1;}c=getchar();}
    while(c>='0'&&c<='9') {f=(f<<3)+(f<<1)+(c&15);c=getchar();}
    f*=fu;
}
template <typename T>
void print(T x)
{
    if(x<0) putchar('-'),x=-x;
    if(x<10) putchar(x+48);
    else print(x/10),putchar(x%10+48);
}
template <typename T>
void print(T x, char t)
{
    print(x);putchar(t);
}
const int maxn=2e5+50;
int dpmax[maxn],dpmin[maxn],a[maxn];
int n;
void solve()
{
    read(n);
    for(int i=1;i<=n;++i)
    read(a[i]);
    int ans=a[1];
    dpmax[1]=dpmin[1]=a[1];
    for(int i=2;i<=n;++i)
    {
        dpmax[i]=max(max(dpmax[i-1]*a[i],dpmin[i-1]*a[i]),a[i]);
        dpmin[i]=min(min(dpmax[i-1]*a[i],dpmin[i-1]*a[i]),a[i]);
        ans=max(ans,dpmax[i]);
    }
    print(ans);
}
int main()
{
    #ifdef AC
    freopen("in.txt","r",stdin);
    freopen("out.txt","w",stdout);
    #endif
    clock_t program_start_clock=clock();
    solve();
    fprintf(stderr,"\nTotal Time: %lf ms",double(clock()-program_start_clock)/(CLOCKS_PER_SEC/1000));
    return 0;
}

C++ 解法, 执行用时: 16ms, 内存消耗: 524KB, 提交时间: 2022-04-05

#include <iostream>
using namespace std;
int main()
{
    int N,firstNeg=1,start = 1;
    int ans=-0x3f3f3f3f,allMul=1,secondMul=1;
    scanf("%d",&N);
    for(int i=1,t;i<=N;++i){
        scanf("%d",&t);
        if(t==0 || i==N+1){
            ans =max(ans,t);
            firstNeg = 1;
            start = 1;
            secondMul = 1;
            allMul = 1;
        }
        else{ 
        if(t<0 && firstNeg==1){
            firstNeg = 2;
            //secondMul=t;
        }
        else if(firstNeg==2){
            secondMul*=t;
            ans = max(ans,secondMul);
        }
        allMul *= t;
        ans = max(ans,allMul);
        //cout<< ans <<endl;
        }
    }
    printf("%d",ans);
    return 0;
}

C 解法, 执行用时: 17ms, 内存消耗: 408KB, 提交时间: 2022-04-05

#include <stdio.h>
int max(int a, int b){
    return a>b?a:b;
}
int main()
{
    int N , ans=-0x3f3f3f3f,allMul=1,secondMul=1,firstNeg=1;
    scanf("%d",&N);
    for(int i=1,t;i<=N;++i){
        scanf("%d",&t);
        if(t==0){
            ans =max(ans,t);
            firstNeg = secondMul =  allMul = 1;
        }
        else{
            if(t<0 && firstNeg==1){
                firstNeg = 2;
            }
            else if(firstNeg==2){
                secondMul*=t;
                ans = max(ans,secondMul);
            }
        allMul *= t;
        ans = max(ans,allMul);
        }
    }
    printf("%d",ans);
    return 0;
}

C++ 解法, 执行用时: 17ms, 内存消耗: 932KB, 提交时间: 2022-07-20

#include <bits/stdc++.h> // C++万能头文件
using namespace std;
static const auto io_sync_off = [](){ // lambda表达式
    std::ios::sync_with_stdio(false); // 解除与scanf()等函数的同步
    std::cin.tie(nullptr); // 解除cin和cout的绑定
    return nullptr;
}();

int main() {
    int curmax = 1, curmin = 1, res = INT_MIN;
    int n;
    cin >> n;
    while (n--) {
        int num;
        cin >> num;
        if (num < 0) // 当前最大值乘以负数为最小，最小值乘以负数为最大
            swap(curmax, curmin);
        curmax = max(curmax * num, num);
        curmin = min(curmin * num, num);
        res = max(res, curmax);
    }
    cout << res << "\n";
    return 0;
}