HDU 1754 I hate it 分段树Segment Tree题解

来源：互联网发布：mp3电路图不用单片机编辑：程序博客网时间：2024/06/06 03:49

给出一段数据，然后要更新单个数据，会询问一段数据中的最大值。

又是一道分段树操作。渐渐熟手了。

#pragma once#include <cstdio>#include <algorithm>using namespace std;class IHateIt_1754_1{static const int SIZE = 200001;int *segTree;//不要使用segTree[SIZE<<2]inline int lChild(int r) { return r<<1; }inline int rChild(int r) { return r<<1|1; }void pushUp(int rt){segTree[rt] = max(segTree[lChild(rt)], segTree[rChild(rt)]);}void build(int l, int r, int rt){if (l == r){scanf("%d", &segTree[rt]);return ;}int m = l + ((r-l)>>1);build(l, m, lChild(rt));build(m+1, r, rChild(rt));pushUp(rt);}void update(const int stu, const int score, int l, int r, int rt){if (l == r){segTree[rt] = score;return ;}int m = l + ((r-l)>>1);if (stu <= m) update(stu, score, l, m, lChild(rt));else update(stu, score, m+1, r, rChild(rt));pushUp(rt);}int query(const int L, const int R, int l, int r, int rt){if (L <= l && r <= R) return segTree[rt];int m = l + ((r-l)>>1);int res = 0;if (L <= m) res = query(L, R, l, m, lChild(rt));//注意下标if (R > m) res = max(res, query(L, R, m+1, r, rChild(rt)));return res;}public:IHateIt_1754_1() : segTree((int *) malloc (sizeof(int) * (SIZE<<2))){int N, M;while (scanf("%d %d", &N, &M) != EOF){build(1, N, 1);while (M--){char op[2];int a, b;scanf("%s%d%d", op, &a, &b); if (op[0] == 'U') update(a, b, 1, N, 1);else printf("%d\n",query(a, b, 1, N, 1));}}}~IHateIt_1754_1(){if (segTree) free(segTree);}};

1 0