HDU3308 LCIS

　　原题传送：http://acm.hdu.edu.cn/showproblem.php?pid=3308

　　线段树，区间合并。

　　节点记录下面变量：
　　int l, r, c;   // 区间左端点、右端点和区间长度
　　int lv, rv;    // 区间左值，右值
　　int lsum, rsum, msum;  // 区间左上升长度，右上升长度，区间最大上升长度

 

View Code

  1 #include <stdio.h>
  2 #include <string.h>
  3 #define lson (cur << 1)
  4 #define rson (cur << 1 | 1)
  5 #define N 100010
  6 
  7 int n, m, a[N];
  8 
  9 inline int max(int x, int y){return x > y ? x : y;}
 10 inline int min(int x, int y){return x < y ? x : y;}
 11 
 12 struct node
 13 {
 14     int l, r, c;           // 区间左端点、右端点和区间长度
 15     int lv, rv;            // 区间左值，右值
 16     int lsum, rsum, msum;  // 区间左上升长度，右上升长度，最大上升长度
 17 }tree[N << 2];
 18 
 19 void pushup(int cur)
 20 {
 21     tree[cur].lv = tree[lson].lv;
 22     tree[cur].rv = tree[rson].rv;
 23     tree[cur].lsum = tree[lson].lsum;
 24     tree[cur].rsum = tree[rson].rsum;
 25     tree[cur].msum = max(tree[lson].msum, tree[rson].msum);
 26     if(tree[lson].rv < tree[rson].lv)
 27     {
 28         if(tree[lson].lsum == tree[lson].c && tree[lson].rv < tree[rson].lv)
 29             tree[cur].lsum += tree[rson].lsum;
 30         if(tree[rson].rsum == tree[rson].c && tree[rson].lv > tree[lson].rv)
 31             tree[cur].rsum += tree[lson].rsum;
 32         
 33         tree[cur].msum = max(tree[cur].msum, tree[lson].rsum + tree[rson].lsum);
 34     }
 35 }
 36 
 37 void update(int cur, int loc, int v)
 38 {
 39     if(tree[cur].l == tree[cur].r)
 40     {
 41         tree[cur].lv = tree[cur].rv = v;
 42         return ;
 43     }
 44     int mid = (tree[cur].l + tree[cur].r) >> 1;
 45     if(mid >= loc)
 46         update(lson, loc, v);
 47     else
 48         update(rson, loc, v);
 49     pushup(cur);
 50 }
 51 
 52 int query(int cur, int l, int r)
 53 {
 54     if(tree[cur].l >= l && tree[cur].r <= r){
 55         return tree[cur].msum;
 56     }
 57     int mid = (tree[cur].l + tree[cur].r) >> 1;
 58     int ans = 0;
 59     if(mid >= l) ans = max(ans, query(lson, l, r));
 60     if(mid < r) ans = max(ans, query(rson, l, r));
 61     if(tree[lson].rv < tree[rson].lv){
 62         ans = max(ans, min(mid - l + 1, tree[lson].rsum) + min(r - mid, tree[rson].lsum));
 63     }
 64     return ans;
 65 }
 66 
 67 void build(int cur, int l, int r)
 68 {
 69     tree[cur].l = l, tree[cur].r = r, tree[cur].c = r - l + 1;
 70     if(l == r)
 71     {
 72         tree[cur].lv = tree[cur].rv = a[l];
 73         tree[cur].lsum = tree[cur].rsum = tree[cur].msum = 1;
 74         return ;
 75     }
 76     int mid = (l + r) >> 1;
 77     build(lson, l, mid);
 78     build(rson, mid + 1, r);
 79     pushup(cur);
 80 }
 81 
 82 int main()
 83 {
 84     int cas, i, x, y;
 85     char op[5];
 86     scanf("%d", &cas);
 87     while(cas --)
 88     {
 89         scanf("%d%d", &n, &m);
 90         for(i = 1; i <= n; i ++)
 91             scanf("%d", &a[i]);
 92         build(1, 1, n);
 93         while(m --)
 94         {
 95             scanf("%s%d%d", op, &x, &y);
 96             if(op[0] == 'Q')
 97             {
 98                 printf("%d\n", query(1, x + 1, y + 1));
 99             }
100             else if(op[0] == 'U')
101             {
102                 update(1, x + 1, y);
103             }
104         }
105     }
106     return 0;
107 }