30 lines
673 B
C++
30 lines
673 B
C++
#include <bits/stdc++.h>
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using namespace std;
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typedef long long LL;
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const int N = 4e5 + 10;
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int n;
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LL a[N], s[N];
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LL ans = -1e18;
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int main() {
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cin >> n;
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for (int i = 1; i <= n; i++) {
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cin >> a[i];
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a[n + i] = a[i];
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}
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for (int i = 1; i <= 2 * n; i++)
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s[i] = s[i - 1] + a[i];
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// 对于每个位置i，枚举它前面n个位置，找最小前缀和
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for (int i = 1; i <= 2 * n; i++) {
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LL minPrefix = s[i - 1]; // 初始化为i-1位置的前缀和
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for (int j = max(0, i - n); j <= i - 2; j++)
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minPrefix = min(minPrefix, s[j]);
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ans = max(ans, s[i] - minPrefix);
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}
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printf("%lld\n", ans);
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return 0;
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} |