Find the nondecreasing subsequences HDU 2227

樹狀數組

#include<iostream>#include<cstdio>#include<cstring>#include<algorithm>using namespace std;#define maxn 100006int a[maxn];int n=maxn;struct Note{int val,ord;}b[maxn];bool cmp(Note a,Note b){return a.val<b.val;}int lowbit(int i){return i&(-i);}int Sum(int i){int sum=0;while(i>=1){sum=(sum+a[i])%1000000007;i-=lowbit(i);}return sum;}void Update(int i,int tem){while(i<=n){a[i]+=tem;a[i]=a[i]%1000000007;i+=lowbit(i);}}int main(){int m;int i;int c[maxn];int k;while(scanf("%d",&m)!=EOF){for(i=1;i<=m;i++){scanf("%d",&b[i].val);b[i].ord=i;}sort(b+1,b+m+1,cmp);memset(a,0,sizeof(a));c[b[1].ord]=1;for(i=2;i<=m;i++)//因為數值範圍是2^32,所以做了個小處理，按照排序把數值縮小。{if(b[i].val>b[i-1].val)c[b[i].ord]=i;elsec[b[i].ord]=c[b[i-1].ord];}for(i=1;i<=m;i++){k=Sum(c[i]);Update(c[i],k+1);}printf("%d\n",Sum(m));}return 0;}