洛谷 P1020 导弹拦截

题目传送门

解题思路:

其实就是求一遍最长不上升子序列和最长上升子序列

AC代码:

#include<iostream>
#include<cstdio>
#include<algorithm> 

using namespace std;

int n,a[100001],f[100001],dp[100001],len = 1,tot = 1,p;

int main() {
    while(scanf("%d",&a[++p]) != EOF);
    f[1] = a[1];
    dp[1] = a[1];
    p--;
    for(int i = 2;i <= p; i++) {
        if(a[i] <= f[len]) 
            f[++len] = a[i];
        else {
            int u = upper_bound(f+1,f+len+1,a[i],greater<int>()) - f;
            f[u] = a[i];
        }
        if(a[i] > dp[tot])
            dp[++tot] = a[i];
        else {
            int o = lower_bound(dp+1,dp+tot+1,a[i]) - dp;
            dp[o] = a[i];
        }
    }
    printf("%d\n%d",len,tot);
    return 0;
}