UVA - 11235 Frequent values 线段树 区间合并

查Bug到凌晨系列，下次一定要写仔细呀。

传送门：http://acm.hust.edu.cn/vjudge/problem/viewProblem.action?id=23846

#include <cstdio>
#include <cstring>
#include <stack>
#include <queue>
#include <iostream>
#include <algorithm>
#include <map>
#include <vector>

using namespace std;

const int MAXN = 100005;

struct Node {
    int x,y;
    int maxlen;
    int llen,rlen;
}t[MAXN<<2];

int a[MAXN];

void Push_Up(int rt) {
    //Update maxlen;
    t[rt].maxlen = max(t[rt<<1].maxlen,t[rt<<1|1].maxlen);
    if(a[t[rt<<1].y] == a[t[rt<<1|1].x])t[rt].maxlen = max(t[rt].maxlen,t[rt<<1].rlen+t[rt<<1|1].llen);

    //Update llen;
    t[rt].llen = t[rt<<1].llen;
    if(t[rt<<1].llen == t[rt<<1].y - t[rt<<1].x + 1 && a[t[rt<<1].y] == a[t[rt<<1|1].x]) 
        t[rt].llen += t[rt<<1|1].llen;

    //Update rlen;
    t[rt].rlen = t[rt<<1|1].rlen;
    if(t[rt<<1|1].rlen == t[rt<<1|1].y - t[rt<<1|1].x + 1 && a[t[rt<<1].y] == a[t[rt<<1|1].x])
         t[rt].rlen += t[rt<<1].rlen;
}

void Build(int x,int y,int  rt) {
    t[rt].x = x; t[rt].y = y; 
    if(x == y) {
        t[rt].maxlen = 1;
        t[rt].llen = 1;
        t[rt].rlen = 1;
        return ;
    }
    int mid = (x + y) >> 1;
    Build(x,mid,rt<<1);
    Build(mid+1,y,rt<<1|1);
    Push_Up(rt);
}

int p;//Last right ;
int ans ;
int tempright;
int tempans;

void Query(int x,int y,int rt,int Left,int Right) {
    if(x >= Left && y <= Right) {
        //Update tempans;
        //printf("x : %d y : %d\n",x,y);
        tempans = t[rt].maxlen;
        //printf("x : %d y : %d maxlen : %d Tempans : %d\n",t[rt].x,t[rt].y,t[rt].maxlen,tempans);
        //printf("tempright : %d\n",tempright);
        if(a[x] == a[p]) {
            //puts("Hello");
            //printf("p : %d a[p] : %d\n",p,a[p]);
            //printf("x : %d\n",x);
            tempans = max(tempans,tempright+t[rt].llen);
            //printf("Tempans : %d\n",tempans);
        }
        //printf("Tempans : %d\n",tempans);
        //Update ans;
        ans = max(ans,tempans);

        //Update tempright;
        if(t[rt].rlen < y - x + 1) tempright = t[rt].rlen;
        else {
            if(a[x] == a[p]) {
                tempright += t[rt].rlen;
            }
            else 
                tempright = t[rt].rlen;
            //Important !!!!!!!
        } 
        //printf("tempright : %d\n",tempright);
        //Update p;
        p = y;

        return ;
    }
    int mid = (x + y) >> 1;
    if(mid >= Left ) Query(x,mid,rt<<1,Left,Right);
    if(mid <  Right) Query(mid+1,y,rt<<1|1,Left,Right);
}

void print(int x,int y,int rt){
    printf("Left : %d Right : %d maxlen : %d llen : %d rlen : %d\n",x,y,t[rt].maxlen,t[rt].llen,t[rt].rlen);
    if(x == y) return ;
    int mid = ( x + y ) >> 1;
    print(x,mid,rt<<1);
    print(mid+1,y,rt<<1|1);
}

void Deal_with() {
    int n,q;
    while(scanf("%d",&n),n) {
        memset(t,0,sizeof(t));
        scanf("%d",&q);
        for(int i = 1 ; i <= n ; i++) {
            scanf("%d",a+i);
          //  printf("%d ",a[i]);
        }
        //puts("");
        Build(1,n,1);
        //print(1,n,1);
        int tempa,tempb;
        for(int i = 1 ; i <= q ; i++) {
            ans = 0; tempans = 0;tempright = 0;
            scanf("%d %d",&tempa,&tempb);
            //printf("%d %d\n",tempa,tempb);
            p = tempa;
            Query(1,n,1,tempa,tempb);
            printf("%d\n",ans);
        }
    }
}

int main(void) {
    //freopen("a.in","r",stdin);
    //freopen("out.txt","w",stdout);
    Deal_with();
}