26 lines
874 B
C++
26 lines
874 B
C++
#include <bits/stdc++.h>
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using namespace std;
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const int INF = 0x3f3f3f3f;
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const int N = 200010;
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int n;
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int a[N];
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//分治函数
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int rec(int l, int r) {
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//递归的出口
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if (l == r) return a[l]; // l=r时，直接返回该位置的值
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int mid = (l + r) >> 1; //中间点
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// [l..mid]区间内包含mid的最大后缀和
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int sum = 0, lmax = -INF, rmax = -INF;
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for (int i = mid; i >= l; i--) sum += a[i], lmax = max(lmax, sum);
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// [mid+1..r]区间内包含(mid+1)的最大前缀和
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sum = 0;
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for (int i = mid + 1; i <= r; i++) sum += a[i], rmax = max(rmax, sum);
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//三种可能取最大值
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return max(max(rec(l, mid), rec(mid + 1, r)), lmax + rmax);
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}
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int main() {
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cin >> n;
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for (int i = 1; i <= n; i++) cin >> a[i];
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printf("%d", rec(1, n)); //在范围1~n之间求最大子段和
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return 0;
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} |