复习线段树

来源：互联网发布：商务中国域名转出编辑：程序博客网时间：2024/06/15 14:40

回归的第一天就听大姐姐的LCT

发现还要先懂WT大哥哥的SPLAY

发现还要先复习一下线段树

发现要复习一下二叉树

发现......

好吧其实没这么多发现

总之线段树又打了一遍

线段树

一、建树

二、查询

三、点修改

四、区间修改

（还要注意一个lazy-tag~~，还是迷迷糊糊的~~）

自己好好理解吧~

#include<cstdio>#include<cstdlib>#include<cstring>#include<iostream>#include<algorithm>//eg.找最小数 using namespace std;#define maxn (1000+10)#define INF 0x7f7f7f7fint a[maxn];struct node{    int val;    int lazy;}seg[maxn*4];void built(int node, int be, int en){seg[node].lazy = 0;if(be == en) seg[node].val = a[be];else{int mid = be+((en-be)>>1);built(node*2, be, mid);built(node*2+1, mid+1, en);seg[node].val = min(seg[node*2].val, seg[node*2+1].val);}}void update_point(int node, int be, int en, int ind, int add){    if(be == en && ind == be){    seg[node].val += add;    return;}int mid = be+((en-be)>>1);if(ind <= mid)update_point(node*2, be, mid, ind, add);else update_point(node*2+1, mid+1, en, ind, add);seg[node].val = min(seg[node*2].val, seg[node*2+1].val);}void pushdown(int node){    if(seg[node].lazy != 0){    seg[node*2].lazy += seg[node].lazy;    seg[node*2+1].lazy += seg[node].lazy;        seg[node*2].val += seg[node].lazy;    seg[node*2+1].val += seg[node].lazy;        seg[node].lazy = 0;}}int query(int node, int be, int en, int le, int ri){if(be > ri || en < le) return INF;if(be >= le && en <= ri) return seg[node].val;pushdown(node);int mid = be+((en-be)>>1);return min(query(node*2, be, mid, le, ri),   query(node*2+1, mid+1, en, le, ri));}void update_interval(int node, int be, int en, int le, int ri, int add){if(be > ri || en < le) return;if(be >= le && en <= ri){    seg[node].lazy += add;    seg[node].val += add;    return;}pushdown(node);int mid = be+((en-be)>>1);update_interval(node*2, be, mid, le, ri, add);update_interval(node*2+1, mid+1, en, le, ri, add);seg[node].val = min(seg[node*2].val, seg[node*2+1].val);}int main(){freopen("segtree.in", "r", stdin);freopen("segtree.out","w",stdout);    int n;scanf("%d", &n);for(int i = 1; i <= n; i++) scanf("%d", &a[i]);built(1, 1, n);int p, q, ans = 0;scanf("%d", &p);for(int i = 1; i <= p; i++){scanf("%d", &q);int x, y, z;if(!q){scanf("%d%d", &x, &y);ans = query(1, 1, n, x, y);printf("%d\n", ans);}else if(q == 1){//point update    scanf("%d%d", &x, &y);    update_point(1, 1, n, x, y);}else if(q == 2){//interval updatescanf("%d%d%d", &x, &y, &z);update_interval(1, 1, n, x, y, z);}}return 0;}

1 0