[luoguP1901] 发射站（单调栈）

传送门

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 = , f = ;
     char ch = getchar();
     for(; !isdigit(ch); ch = getchar()) if(ch == '-') f = -;
     for(; isdigit(ch); ch = getchar()) x = (x << ) + (x << ) + ch - '';
     return x * f;
 }
 
 int main()
 {
     int i;
     n = read();
     for(i = ; i <= n; i++) a[i] = read(), b[i] = read();
     a[] = a[n + ] = 1e9;
     for(i = ; i <= n + ; i++)
     {
         while(t && a[s[t]] < a[i]) sum[i] += b[s[t--]];
         s[++t] = i;
     }
     t = ;
     for(i = n; i >= ; i--)
     {
         while(t && a[s[t]] < a[i]) sum[i] += b[s[t--]];
         s[++t] = i;
     }
     for(i = ; i <= n; i++) ans = max(ans, sum[i]);
     printf("%lld\n", ans);
 }