hdu 1754 i hate it（线段树入门）

 

http://acm.hdu.edu.cn/showproblem.php?pid=1754

 

解题思路：线段树啦

 

#include <stdio.h>#include <string.h>#define GetMax(a,b) a>b?a:b#define size 200001struct seg_tree {int left,right;int max;}tree[size*4];int val[size],N,M;void build(int num,int left,int right){tree[num].left = left;tree[num].right = right;if(right-left>1){int mid = (left+right)>>1;build(2*num,left,mid);build(2*num+1,mid,right);tree[num].max = GetMax(tree[2*num].max,tree[2*num+1].max);}else tree[num].max = GetMax(val[left],val[right]);}void InputData(){int i;for(i=1;i<=N;i++)scanf("%d",&val[i]);scanf("%d",&M);}void update(int num,int locate){if (tree[num].right-tree[num].left==1){tree[num].max = GetMax(val[tree[num].right],val[tree[num].left]);return;}int mid = (tree[num].left+tree[num].right)>>1;if (locate<=mid)update(2*num,locate);if(locate>=mid)update(2*num+1,locate);tree[num].max = GetMax(tree[2*num].max,tree[2*num+1].max);}int query(int num,int left,int right){if(tree[num].left==left&&tree[num].right==right)return tree[num].max;int mid = (tree[num].left+tree[num].right)>>1;if(right<=mid)return query(2*num,left,right);else if(left>=mid)return query(2*num+1,left,right);else{int max1,max2;max1 = query(2*num,left,mid);max2 = query(2*num+1,mid,right);return GetMax(max1,max2);}}int main(){char s[2];int a,b;while (scanf("%d%d",&N,&M)!=EOF){InputData();build(1,1,N);while (M--){scanf("%s%d%d",s,&a,&b);if (s[0]=='Q')printf("%d/n",query(1,a,b));elseval[a] = b,update(1,a);}}return 0;}