HDU 1754 I Hate it (線段樹最大值模板)

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思路：與我發表的上一遍求和的思想一樣   只是現在變成求最大值而已

AC代碼：

#include<iostream>#include<cstdio>#include<cmath>#include<cstring>#include<algorithm>using namespace std;inline int Max(int a, int b){return a > b ? a : b;}const int MAXN = 200001; // 區間範圍struct{int l, r, m; // l 左端點，r 右端點，m 為該區間的最大分數} tree[MAXN*4];int a[MAXN];void creat(int t, int l, int r){tree[t].l = l, tree[t].r = r;if(l == r) // 葉子節點{tree[t].m = a[l];return; //遞迴出口}int m = (l+r) / 2;creat(t*2, l, m), creat(t*2+1, m+1, r); // 左孩子tree[t].m = Max(tree[t*2].m, tree[t*2+1].m); // 右孩子}void update(int t, int n, int v) // 把n 點的值更新為v{if(tree[t].l == tree[t].r && tree[t].l == n){tree[t].m = v;return;}if(n <= tree[t*2].r) update(t*2, n, v);else update(t*2+1, n, v);tree[t].m = Max(tree[t*2].m, tree[t*2+1].m);}int query(int t, int l, int r) // 查詢t 節點在【l，r】區間範圍的最大值{if(l == tree[t].l && r == tree[t].r) return tree[t].m;int s;if(r <= tree[t*2].r) s = query(t*2, l, r);else if(l >= tree[t*2+1].l) s= query(t*2+1, l, r);else s = Max(query(t*2, l, tree[t*2].r), query(t*2+1, tree[t*2+1].l, r));return s;}int main(){int n, m, i, x1, x2;char s[2];while(scanf("%d%d", &n, &m) != EOF){for(i = 1; i <= n; i++) scanf("%d", &a[i]);creat(1, 1, n); // 根節點標號為1，區間為【1，n】while(m--){scanf("%s%d%d", s, &x1, &x2);if(s[0] == 'Q') printf("%d\n", query(1, x1, x2)); // 查詢else update(1, x1, x2); // 更新}}return 0;}