POJ(2761)Feed the dogs (树状数组+离散化+贪心)

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#include <iostream>#include <algorithm>#include <stdio.h>#include <string>#include <string.h>#include <stdlib.h>#include <math.h>#include <vector>#include <map>#include <queue>#include <stack>#include <set>using namespace std ;const int maxn = 100002;struct dog{    int value;    int id;    friend bool operator<(const dog &a,const dog &b){        return a.value<b.value;    }}dog[maxn];int has[maxn];int dog_value[maxn];struct feed{    int l,r,k;    int id;    friend bool operator<(const feed &a,const feed &b){        if(a.l == b.l)            return a.r<b.r;        return a.l<b.l;    }}feed[maxn/2];int n,m;int c[maxn];int ans[maxn/2];int lowbit(int x){    return x&(-x);}void update(int id,int val){    for(int i = id;i < maxn;i += lowbit(i))        c[i] += val;}int find_kth(int k){    int ans = 0,cnt = 0;    for(int i = 20;i >= 0;i--){        ans += (1<<i);        if(ans >= maxn || cnt + c[ans] >= k)            ans -= (1<<i);        else            cnt += c[ans];    }    return ans+1;}int main(){    while(~scanf("%d%d",&n,&m)){        for(int i = 1;i <= n;i++){            scanf("%d",&dog[i].value);            dog[i].id = i;        }        sort(dog+1,dog+n+1);        dog_value[1] = dog[1].value;        has[dog[1].id] = 1;        for(int i = 2,j = 1;i <= n;i++){            if(dog[i].value != dog[i-1].value)                dog_value[++j] = dog[i].value;            has[dog[i].id] = j;        }        //for(int i = 1;i <= n;i++)          //  printf("%d %d\n",has[i],dog_value[i]);        for(int i = 1;i <= m;i++){            scanf("%d%d%d",&feed[i].l,&feed[i].r,&feed[i].k);            feed[i].id = i;        }        sort(feed+1,feed+m+1);        //for(int i = 1;i <= m;i++)          //  printf("%d %d %d\n",feed[i].l,feed[i].r,feed[i].k);        feed[0].l=1;feed[0].r=0;        for(int i=1;i<=m;i++){            for(int j=feed[i-1].l;j<=feed[i-1].r&&j<feed[i].l;j++)                update(has[j],-1);            for(int j=feed[i].l<feed[i-1].r+1?feed[i-1].r+1:feed[i].l;j<=feed[i].r;j++)                update(has[j],1);            int num=find_kth(feed[i].k);            ans[feed[i].id]=dog_value[num];        }        for(int i = 1;i <= m;i++)            printf("%d\n",ans[i]);    }    return 0;}
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