pku 3264 Balanced Lineup線段樹

第一次在pku做題，囧死了，這麼一道題調了我N久

不過聽說用RMQ-ST演算法更高效，我用線段樹做居然是4047ms

有點讓我驚訝，居然可以慢成這樣~~~~~~~~~

 

#include<stdio.h><br />#define N 50005</p><p>struct node{<br /> int l;<br /> int r;<br /> int min;<br /> int max;<br />};</p><p>node tree[3*N];<br />int arr[N];</p><p>void buid_tree(int k,int left,int right)<br />{<br />int mid;<br />int L,R;<br />tree[k].l = left; tree[k].r = right;<br />if(right-left == 1){<br />tree[k].min = tree[k].max = arr[left];<br />return ;<br />}<br />L = 2*k; R = L+1;<br />mid = (tree[k].l+tree[k].r)/2;<br />buid_tree(L,left,mid);<br />buid_tree(R,mid,right);<br />tree[k].min = tree[L].min > tree[R].min? tree[R].min:tree[L].min;<br />tree[k].max = tree[L].max > tree[R].max? tree[L].max:tree[R].max;<br />return ;<br />}</p><p>int tree_search_min(int k,int left,int right)<br />{<br />int mid;<br />int L,R;<br />int lm = 1000005,rm = 1000005;<br />if(left <= tree[k].l && right >= tree[k].r){<br /> return tree[k].min;<br />}<br />L = 2*k; R = L+1;<br />mid = (tree[k].l+tree[k].r)/2;<br />if(left < mid) lm = tree_search_min(L,left,right);<br />if(right > mid) rm = tree_search_min(R,left,right);<br />return lm < rm? lm:rm;<br />}</p><p>int tree_search_max(int k,int left,int right)<br />{<br />int mid;<br />int L,R;<br />int lm = 0,rm = 0;<br />if(left <= tree[k].l && right >= tree[k].r){<br /> return tree[k].max;<br />}<br />L = 2*k; R = L+1;<br />mid = (tree[k].l+tree[k].r)/2;<br />if(left < mid) lm = tree_search_max(L,left,right);<br />if(right > mid) rm = tree_search_max(R,left,right);<br />return lm > rm? lm:rm;<br />}</p><p>int main()<br />{<br />int n,q;<br />int i;<br />int a,b;<br />while(scanf("%d %d",&n,&q) == 2){<br /> for(i = 1;i <= n;i++)<br />scanf("%d",arr+i);<br />buid_tree(1,1,n+1);<br />for(i = 0;i < q;i++){<br /> scanf("%d %d",&a,&b);<br /> printf("%d/n",tree_search_max(1,a,b+1)-tree_search_min(1,a,b+1));<br />}<br />}<br />return 0;<br />}