HDU 4970 Killing Monsters(扫描线)

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比赛的时候没仔细考虑，看了题目就直接上线段树，不出所料TLE，许久后改用树状数组，875ms过。比赛后才想起可以用扫描线的办法去做。。我问某胖他怎么做的。。。他说就是用你上次说的那方法做的。。T_T。

话说也知道了个道理。如果不是一边更新一边查询完全没必要用线段树或者树状数组。没必要。。线段树后来A了。加了读入优化900多ms。。当时比赛用了就早水过了。

放2个AC代码（都丧心病狂用了读入优化。加了能优化近600ms）：

树状数组的：

#include <iostream>#include <cstdio>#include <string.h>#include <string>#include <algorithm>#include <cmath>using namespace std;#define ll __int64const int maxn=100005;#define lson l,mid,rt<<1#define rson mid+1,r,rt<<1|1inline void scan_d(int &ret){    char c; ret=0;    while((c=getchar())<'0'||c>'9');    while(c>='0'&&c<='9') ret=ret*10+(c-'0'),c=getchar();}ll b[maxn],c[maxn];int n;void add_b(int x,int k){    for(int i = x; i >0; i -= i&(-i)) b[i]+=k;}void add_c(int x, int k){    for(int i = x; i <= n; i += i&(-i)) c[i] += x*k;}ll sum_b(int x){    ll s = 0;    for(int i = x; i <= n; i+= i&(-i)) s+=b[i];    return s;}ll sum_c(int x){    ll s = 0;    for(int i = x; i > 0; i -= i&(-i)) s+=c[i];    return s;}inline ll sum(int x){    if(x) return sum_b(x)*x+sum_c(x-1);    else return 0;}int main(){//    freopen("1.txt","r",stdin);    int m,i,k;    while(~scanf("%d",&n)&&n)    {//        scanf("%d",&m);        scan_d(m);        memset(b,0,sizeof(b));        memset(c,0,sizeof(c));        int l,r;        for(i = 0; i < m; i++)        {//            scanf("%d%d%d",&l,&r,&k);            scan_d(l); scan_d(r); scan_d(k);            int newl = n-r+1,newr = n-l+1;            add_b(newr,k);            add_c(newr,k);            if(newl > 1)            {                add_b(newl-1,-k);                add_c(newl-1,-k);            }        }        scanf("%d",&m);        int ans = 0;        ll sum1,h;        for(i = 0; i < m; i++)        {            scanf("%I64d",&h);            scan_d(l);            sum1 = sum(n-l+1);            if(sum1 < h) ans++;//            cout<<sum1<<endl;        }        printf("%d\n",ans);    }    return 0;}

扫描线：

#include<cstdio>#include<ctype.h>#include<algorithm>#include<iostream>#include<cstring>#include<vector>#include<cstdlib>#include<stack>#include<cmath>#include<queue>#include<set>#include<ctime>#include<string.h>#include<string>using namespace std;#define ll __int64#define eps 1e-8ll a[100005];template<class T>inline void scan_d(T &ret) {    char c; ret=0;    while((c=getchar())<'0'||c>'9');    while(c>='0'&&c<='9') ret=ret*10+(c-'0'),c=getchar();}int main(){    #ifdef GLQ    freopen("1011.in","r",stdin);//    freopen("o.txt","w",stdout);    #endif // GLQ    int n,m,i;    while(~scanf("%d",&n)&&n)    {        memset(a,0,sizeof(a));        scan_d(m);        for(i = 0; i < m; i++)        {            int l,r,k;            scan_d(l);scan_d(r);scan_d(k);//            scanf("%d%d%d",&l,&r,&k);            a[l-1] -= k;            a[r] += k;        }        ll flag = 0;        for(i = n; i >= 0; i--)        {            flag += a[i];            a[i] = flag+a[i+1];        }        scan_d(m);        int ans = 0;        for(i = 0; i < m; i++)        {            ll h;int l;            scan_d(h);scan_d(l);//            scanf("%I64d%d",&h,&l);            if(h > a[l]) ans++;        }        printf("%d\n",ans);    }    return 0;}

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