BZOJ1109 [POI2007]堆积木Klo

随便推推，发现要求求a[i]-i单调不降，a[i]单调递增的最长子序列

然后发现这两个条件可以推出i<j

所以改变一下坐标然后求最长上升子序列即可

注意双关键字排序

注意吧a[i]-i>0的都continue了

#include<iostream>
#include<cstring>
#include<ctime>
#include<cmath>
#include<algorithm>
#include<iomanip>
#include<cstdlib>
#include<cstdio>
#include<map>
#include<bitset>
#include<set>
#include<stack>
#include<vector>
#include<queue>
using namespace std;
#define MAXN 100010
#define MAXM 1000010
#define ll long long
#define eps 1e-8
#define MOD 1000000007
#define INF 1000000000
#define lb(x) x&-x
struct data{
int x;
int y;
friend bool operator <(data x,data y){
return x.x!=y.x?x.x>y.x:x.y<y.y;
}
};
data a[MAXN];
int n;
int c[MAXM];
int ans;
void change(int x,int y){
for(;x<MAXM;x+=lb(x)){
c[x]=max(c[x],y);
}
}
int ask(int x){
int re=0;
for(;x;x-=lb(x)){
re=max(re,c[x]);
}
return re;
}
int main(){
int i,x;
scanf("%d",&n);
for(i=1;i<=n;i++){
scanf("%d",&x);
a[i].x=x-i;
a[i].y=x;
}
sort(a+1,a+n+1);
for(i=1;i<=n;i++){
if(a[i].x>0){
continue ;
}
x=ask(a[i].y-1)+1;
ans=max(ans,x);
change(a[i].y,x);
}
printf("%d\n",ans);
return 0;
}

/*

*/