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#include <bits/stdc++.h>
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using namespace std;
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const int N = 1e5 + 10;
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const int INF = 0x3f3f3f3f;
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int n;
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int w[N];
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int f[N][2];//考虑前i天的股市，第i天的手中股票状态为j(j=0 未持股，j=1 持股)
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int main() {
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cin >> n;
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for (int i = 1; i <= n; i++)cin >> w[i];
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/**
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因为f[0][1]代表考虑前0天，状态是已经买入，这是一个不合法状态。(一般不合法的状态设置为INF或者-INF，要看取最大值或最小值)
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第一次买入至少是在第1天。
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如果不把它初始化为负无穷，f[1][0]就会更新成f[0][1] + w[1]，也就是w[1]
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但是f[1][0]实际意义是第 1 天不买入股票，那么收益就是 0，而不是w[i]
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*/
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f[0][1] = -INF;
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for (int i = 1; i <= n; i++) {
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f[i][0] = max(f[i - 1][0], f[i - 1][1] + w[i]);
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f[i][1] = max(f[i - 1][1], f[i - 1][0] - w[i]);
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}
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printf("%d\n", f[n][0]);
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return 0;
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}
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