hdu5316 线段树

来源：互联网发布：群星公主号知乎编辑：程序博客网时间：2024/06/08 15:47

题意有点难懂
找一个区间中奇偶交替的子序列的最大值
奇偶交替可以是以奇数开头奇数结尾
奇数开头偶数结尾
偶数开头偶数结尾
偶数开头奇数结尾
四种情况

还有就是单点更新维护线段树

#include <queue>#include <stack>#include <deque>#include <math.h>#include <string>#include <vector>#include <stdio.h>#include <iostream>#include <string.h>#include <algorithm>#include <functional>#define mem(a) memset(a,0,sizeof(a));#define mem_1(a) memset(a,-1,sizeof(a));#define sf(a) scanf("%d",&a)#define sff(a,b) scanf("%d%d",&a,&b)#define sfff(a,b,c) scanf("%d%d%d",&a,&b,&c)#define lson l,mid,i<<1#define LL long long#define rson mid+1,r,i<<1|1const LL INF = 1100000000000;const int MAXN = 100500;const double PI = acos(-1.0);const double esp = 1e-10;using namespace std;struct node{    int l,r;LL oo,jj,oj,jo,num;   // int mid(){return (l+r)>>1;}}Tree[MAXN<<2];LL max(LL a,LL b){    return a>b ? a:b;}void pushUp(int i){Tree[i].jj = max(max(max(Tree[i<<1].jj, Tree[i<<1|1].jj),Tree[i<<1].jj + Tree[i<<1|1].oj),Tree[i<<1].jo + Tree[i<<1|1].jj);Tree[i].oo = max(max(max(Tree[i<<1].oo, Tree[i<<1|1].oo),Tree[i<<1].oj + Tree[i<<1|1].oo),Tree[i<<1].oo + Tree[i<<1|1].jo);Tree[i].jo = max(max(max(Tree[i<<1].jo, Tree[i<<1|1].jo),Tree[i<<1].jo + Tree[i<<1|1].jo),Tree[i<<1].jj + Tree[i<<1|1].oo);Tree[i].oj = max(max(max(Tree[i<<1].oj, Tree[i<<1|1].oj),Tree[i<<1].oo + Tree[i<<1|1].jj),Tree[i<<1].oj + Tree[i<<1|1].oj);}void build_tree(int l,int r,int i){Tree[i].l = l;Tree[i].r = r;if(l == r){//sf(Tree[i].num);scanf("%I64d",&Tree[i].num);if(l%2){Tree[i].jj = Tree[i].num;Tree[i].oo = -INF;}else{Tree[i].oo = Tree[i].num;Tree[i].jj = -INF;}Tree[i].jo = Tree[i].oj = -INF;return ;}int  mid = (l+r)>>1 ;build_tree(lson);build_tree(rson);pushUp(i);}void updata_tree(int pos,LL num,int i){if(Tree[i].l == pos && Tree[i].r == pos){Tree[i].num = num;if(Tree[i].l%2){Tree[i].jj = Tree[i].num;Tree[i].oo = -INF;}else{Tree[i].oo = Tree[i].num;Tree[i].jj = -INF;}Tree[i].jo = Tree[i].oj = -INF;return ;}int  mid = (Tree[i].l+Tree[i].r) >> 1;if(pos <= mid) updata_tree(pos,num,i<<1);else updata_tree(pos,num,i<<1|1);pushUp(i);}node Query(int l,int r,int i){if(l == Tree[i].l && r == Tree[i].r)return Tree[i];int  mid = (Tree[i].l+Tree[i].r) >> 1;if(r <= mid) return Query(l,r,i<<1);else if(mid < l) return Query(l,r,i<<1|1);else{struct node ans1 = Query(l,mid,i<<1);struct node ans2 = Query(mid+1,r,i<<1|1);struct node ans;ans.oo = max(max(max(ans1.oo,ans2.oo),ans1.oj+ans2.oo),ans1.oo + ans2.jo);ans.jj = max(max(max(ans1.jj,ans2.jj),ans1.jo+ans2.jj),ans1.jj + ans2.oj);ans.oj = max(max(max(ans1.oj,ans2.oj),ans1.oo+ans2.jj),ans1.oj + ans2.oj);ans.jo = max(max(max(ans1.jo,ans2.jo),ans1.jo+ans2.jo),ans1.jj + ans2.oo);return ans;}}int main(){int T,n,m;sf(T);while(T--){sff(n,m);build_tree(1,n,1);while(m--){    int x;sf(x);if(x == 0){int from,to;scanf("%d%d",&from,&to);struct node ans = Query(from,to,1);printf("%I64d\n",max(max(max(ans.oo,ans.jj),ans.oj),ans.jo) );}else{    int pos;    LL num;scanf("%d%I64d",&pos,&num);updata_tree(pos,num,1);}}}return 0;}

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