线段树 - 3264 Balanced Lineup
大略的的看了线段树的定义然后就开始练手, 可能很多地方可以优化, 仅供参考.
徘徊在AC的边缘, 提交代码要把cout/cin 缓存 printf/scanf 刚好能过.
1 #include <iostream> 2 using namespace std; 3 4 #define MAXN 50010 5 6 struct Node{ 7 int left,right; 8 int max,min; 9 Node * pleft,*pright; 10 Node():pleft(NULL),pright(NULL){} 11 Node(int l,int r):left(l),right(r),max(-1),min(0x7fffffff),pleft(NULL),pright(NULL){} 12 }; 13 14 struct Point{ 15 int min; 16 int max; 17 Point(int ma,int mi):max(ma),min(mi){}; 18 }; 19 20 int heights[MAXN]; 21 22 void build(Node*p){ 23 if(p->left == p->right){ 24 p->max = heights[p->left]; 25 p->min = p->max; 26 return; 27 } 28 //calc the max and min value. 29 for (int i=p->left;i<=p->right;++i){ 30 if(heights[i]>p->max) 31 p->max = heights[i]; 32 if(heights[i]<p->min) 33 p->min = heights[i]; 34 } 35 int mid = (p->left + p->right) >> 1; 36 p->pleft = new Node(p->left,mid); 37 build(p->pleft); 38 p->pright= new Node(mid+1,p->right); 39 build(p->pright); 40 } 41 42 Point query(Node * p, int left,int right){ 43 if(left==p->left && right == p->right) 44 return Point(p->max,p->min); 45 int mid = (p->left+p->right) >> 1; 46 if(left > mid) 47 return query(p->pright,left,right); 48 else if(right <= mid) 49 return query(p->pleft,left,right); 50 else{ 51 Point pl = query(p->pleft,left,mid); 52 Point pr = query(p->pright,mid+1,right); 53 int tmin = pl.min < pr.min ? pl.min : pr.min; 54 int tmax = pl.max > pr.max ? pl.max : pr.max; 55 return Point(tmax,tmin); 56 } 57 } 58 59 60 // for debug. 61 void dfs(Node * p){ 62 if(p == NULL) 63 return; 64 cout<<"DFS TO: ["<<p->left<<", "<<p->right<<"] , ("<<p->max<<", "<<p->min<<")"<<endl; 65 dfs(p->pleft); 66 dfs(p->pright); 67 } 68 int main(){ 69 int N,Q; 70 cin>>N>>Q; 71 for(int i=0;i<N;++i){ 72 cin>>heights[i]; 73 } 74 Node * head = new Node(0,N-1); 75 build(head); 76 // dfs(head); 77 78 int l,r; 79 for(int i=0;i<Q;++i){ 80 cin>>l>>r; 81 Point point = query(head,l-1,r-1); 82 cout<<point.max - point.min<<endl; 83 } 84 return 0; 85 }
AC代码:
#include <stdio.h> #define MAXN 50010 struct Node{ int left,right; int max,min; Node * pleft,*pright; Node():pleft(NULL),pright(NULL){} Node(int l,int r):left(l),right(r),max(-1),min(0x7fffffff),pleft(NULL),pright(NULL){} }; struct Point{ int min; int max; Point(int ma,int mi):max(ma),min(mi){}; }; int heights[MAXN]; void build(Node*p){ if(p->left == p->right){ p->max = heights[p->left]; p->min = p->max; return; } //calc the max and min value. for (int i=p->left;i<=p->right;++i){ if(heights[i]>p->max) p->max = heights[i]; if(heights[i]<p->min) p->min = heights[i]; } int mid = (p->left + p->right) >> 1; p->pleft = new Node(p->left,mid); build(p->pleft); p->pright= new Node(mid+1,p->right); build(p->pright); } Point query(Node * p, int left,int right){ if(left==p->left && right == p->right) return Point(p->max,p->min); int mid = (p->left+p->right) >> 1; if(left > mid) return query(p->pright,left,right); else if(right <= mid) return query(p->pleft,left,right); else{ Point pl = query(p->pleft,left,mid); Point pr = query(p->pright,mid+1,right); int tmin = pl.min < pr.min ? pl.min : pr.min; int tmax = pl.max > pr.max ? pl.max : pr.max; return Point(tmax,tmin); } } // for debug. // void dfs(Node * p){ // if(p == NULL) // return; // cout<<"DFS TO: ["<<p->left<<", "<<p->right<<"] , ("<<p->max<<", "<<p->min<<")"<<endl; // dfs(p->pleft); // dfs(p->pright); // } int main(){ int N,Q; scanf("%d%d",&N,&Q); for(int i=0;i<N;++i){ scanf("%d",&heights[i]); } Node * head = new Node(0,N-1); build(head); // dfs(head); int l,r; for(int i=0;i<Q;++i){ scanf("%d%d",&l,&r); Point point = query(head,l-1,r-1); printf("%d\n",point.max - point.min); } return 0; }
