[luoguP1901] 发射站（单调栈）

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呵呵

——代码

#include <cstdio>
#include <iostream>
#define N 1000010
#define LL long long
#define max(x, y) ((x) > (y) ? (x) : (y))

int n, t, a[N], s[N];
LL ans, b[N], sum[N];

inline LL read()
{
    LL x = 0, f = 1;
    char ch = getchar();
    for(; !isdigit(ch); ch = getchar()) if(ch == '-') f = -1;
    for(; isdigit(ch); ch = getchar()) x = (x << 1) + (x << 3) + ch - '0';
    return x * f;
}

int main()
{
    int i;
    n = read();
    for(i = 1; i <= n; i++) a[i] = read(), b[i] = read();
    a[0] = a[n + 1] = 1e9;
    for(i = 1; i <= n + 1; i++)
    {
        while(t && a[s[t]] < a[i]) sum[i] += b[s[t--]];
        s[++t] = i;
    }
    t = 0;
    for(i = n; i >= 0; i--)
    {
        while(t && a[s[t]] < a[i]) sum[i] += b[s[t--]];
        s[++t] = i;
    }
    for(i = 1; i <= n; i++) ans = max(ans, sum[i]);
    printf("%lld
", ans);
}