2016秋季练习

来源：lightOJ1339

线段树，要维护的东西比较多，但是稍微想想还是可做的

代码：

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#define lson rt<<1
#define rson rt<<1|1
using namespace std;
const int MAXN = 100010;
int a[MAXN];
struct Segment{
    int l,r;
    int lsum,lc;
    int rsum,rc;
    int sum;
}tree[MAXN<<2];
inline void pushup(int rt) {
    int len = tree[rt].r - tree[rt].l + 1;
    if(tree[lson].rc != tree[rson].lc) {
        tree[rt].sum = max(tree[lson].sum,tree[rson].sum);
    }
    else {
        int sum = tree[lson].rsum + tree[rson].lsum;
        tree[rt].sum = max(sum,max(tree[lson].sum,tree[rson].sum));
    }
    tree[rt].lc = tree[lson].lc;
    tree[rt].rc = tree[rson].rc;
    tree[rt].lsum = tree[lson].lsum;
    tree[rt].rsum = tree[rson].rsum;
    if(tree[rt].lsum == ((len+1)>>1) && tree[rson].lc == tree[lson].rc) tree[rt].lsum += tree[rson].lsum;
    if(tree[rt].rsum == (len>>1) && tree[lson].rc == tree[rson].lc) tree[rt].rsum += tree[lson].rsum;
}
void build(int rt,int l,int r){
    tree[rt].l = l;
    tree[rt].r = r;
    tree[rt].lsum = tree[rt].rsum = tree[rt].sum = 0;
    tree[rt].lc = tree[rt].rc  = 0;
    if(l == r) {
        int x;
        scanf("%d",&x);
        tree[rt].lsum = tree[rt].rsum = tree[rt].sum = 1;
        tree[rt].lc = tree[rt].rc  = x;
        return ;
    }
    int mid = (l + r) >> 1;
    build(lson,l,mid);
    build(rson,mid+1,r);
    pushup(rt);
}
int query(int rt,int l,int r){
    if(l <= tree[rt].l && tree[rt].r <= r){
        return tree[rt].sum;
    }
    int res = 0;
    int mid = (tree[rt].l + tree[rt].r) >> 1;
    if(l <= mid) res = max(res,query(lson,l,r));
    if(r  > mid) res = max(res,query(rson,l,r));
    if(tree[lson].rc == tree[rson].lc) {
        int tmpa = min(tree[lson].rsum,mid-l+1);
        int tmpb = min(tree[rson].lsum,r-mid);
        res = max(res,tmpa+tmpb);
    }
    return res;
}
int main(){
    int T,nc = 1;
    scanf("%d",&T);
    while(T--){
        int n,c,Qm;
        scanf("%d%d%d",&n,&c,&Qm);
        build(1,1,n);
        printf("Case %d:\n",nc++);
        while(Qm--) {
            int l,r;
            scanf("%d%d",&l,&r);
            printf("%d\n",query(1,l,r));
        }
    }
    return 0;
}