【线段树】 HDOJ 5091 Beam Cannon

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线段树+扫描线，线段树记录区间最大值就行了。。。
#include <iostream>#include <queue> #include <stack> #include <map> #include <set> #include <bitset> #include <cstdio> #include <algorithm> #include <cstring> #include <climits>#include <cstdlib>#include <cmath>#include <time.h>#define maxn 80005#define maxm 1005#define eps 1e-10#define mod 1000000007#define INF 999999999#define lowbit(x) (x&(-x))#define mp make_pair#define ls o<<1#define rs o<<1 | 1#define lson o<<1, L, mid #define rson o<<1 | 1, mid+1, R#pragma comment(linker, "/STACK:16777216")typedef long long LL;typedef unsigned long long ULL;//typedef int LL;using namespace std;LL qpow(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base;base=base*base;b/=2;}return res;}LL powmod(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base%mod;base=base*base%mod;b/=2;}return res;}void scanf(int &__x){__x=0;char __ch=getchar();while(__ch==' '||__ch=='\n')__ch=getchar();while(__ch>='0'&&__ch<='9')__x=__x*10+__ch-'0',__ch = getchar();}LL gcd(LL _a, LL _b){if(!_b) return _a;else return gcd(_b, _a%_b);}// headstruct point{    int x, y;}p[maxn];int maxv[maxn << 2];int mark[maxn << 2];int n, w, h;int cmp(point a, point b){    return a.y < b.y;}void debug(void){    for(int i = 1; i <= n; i++) printf("%d %d BB\n", p[i].x, p[i].y);}void read(void){    scanf("%d%d", &w, &h);    for(int i = 1; i <= n; i++) {        scanf("%d%d", &p[i].x, &p[i].y);        p[i].x += 20001;        p[i].y += 20001;    }    sort(p+1, p+n+1, cmp);}void init(void){    memset(maxv, 0, sizeof maxv);    memset(mark, 0, sizeof mark);}void pushdown(int o){    if(!mark[o]) return;    maxv[ls] += mark[o];    maxv[rs] += mark[o];    mark[ls] += mark[o];    mark[rs] += mark[o];    mark[o] = 0;}void pushup(int o){    maxv[o] = max(maxv[ls], maxv[rs]);}void updata(int o, int L, int R, int ql, int qr, int x){    if(ql <= L && qr >= R) {        maxv[o] += x;        mark[o] += x;        return;    }    pushdown(o);    int mid = (L + R) >> 1;    if(ql <= mid) updata(lson, ql, qr, x);    if(qr > mid) updata(rson, ql, qr, x);    pushup(o);}void work(void){    int ans = 0;    for(int i = 1, j = 1; i <= n; i++) {        updata(1, 1, 80001, p[i].x, p[i].x + w, 1);        while(p[i].y - p[j].y > h) updata(1, 1, 80001, p[j].x, p[j].x + w, -1), j++;        ans = max(ans, maxv[1]);    }    printf("%d\n", ans);}int main(void){    while(scanf("%d", &n), n >= 0) {        init();        read();        work();    }    return 0;}
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