hdu 1754 I Hate It(树状数组 | 线段树）

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题目链接：hdu 1754 I Hate It

题目大意：略。

解题思路：

方法一：树状数组，注意查询的时候，如果为一个的时候要与当前的数进行比较。

#include <stdio.h>#include <string.h>#include <algorithm>using namespace std;const int N = 200005;int n, m, b[N], v[N];void add(int x, int val) {v[x] = val;while (x <= n) {b[x] = max(val, b[x]);x += (x & (-x));}}void init() {int a;memset(b, 0, sizeof(b));for (int i = 1; i <= n; i++) {scanf("%d", &a);add(i, a);}}int query(int l, int r) {int ans = v[r];while (l != r) {for (r -= 1; r - (r&(-r)) >= l; r -= (r&(-r))) {ans = max(ans, b[r]);}ans = max(ans, v[r]);}return ans;}void solve() {int a, b;char o[10];for (int i = 0; i < m; i++) {scanf("%s%d%d", o, &a, &b);if (o[0] == 'U') add(a, b);else printf("%d\n", query(a, b));}}int main() {while (scanf("%d%d", &n, &m) == 2) {init();solve();}return 0;}

方法二：裸线段树，更新区间查询区间。

#include <stdio.h>#include <string.h>#include <algorithm>using namespace std;const int N = 200005;struct node {int l, r, v;}s[N*3];int n, m;void build(int l, int r, int f) {if (l != r) {int mid = (l + r) / 2;build(l, mid, 2*f);build(mid+1, r, 2*f+1);}s[f].l = l; s[f].r = r; s[f].v = 0;}int insert(int l, int r, int val, int f) {if (s[f].l == s[f].r) {s[f].v = val; return val;} else {int mid = (s[f].l + s[f].r) / 2, c;if (l <= mid && r > mid) { s[f].v = max(insert(l, mid, val, f*2), insert(mid+1, r, val, f*2+1)); }else if (l <= mid && r <= mid) s[f].v = max(insert(l, r, val, f*2), s[f*2+1].v);else s[f].v = max(insert(l, r, val, f*2+1), s[f*2].v);return s[f].v;}}int query(int l, int r, int f) {if (s[f].l == l && s[f].r == r) return s[f].v;int mid = (s[f].l + s[f].r) / 2;if (l <= mid && r > mid) return max(query(l, mid, f*2), query(mid+1, r, f*2+1));else if (l <= mid && r <= mid) return query(l, r, f*2);else return query(l, r, f*2+1);}void init() {build(1, n, 1);int a;for (int i = 1; i <= n; i++) {scanf("%d", &a);insert(i, i, a, 1);}}int main() {int a, b;char o[10];while (scanf("%d%d", &n, &m) == 2) {init();for (int i = 0; i < m; i++) {scanf("%s%d%d", o, &a, &b);if (o[0] == 'Q') printf("%d\n", query(a, b, 1));else insert(a, a, b, 1);}}return 0;}

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