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  第二道線段樹，哈哈哈，已經從區間求和萌萌噠變成求最大值，我是不是好無聊哦~~~~

代碼：

 1 #include <cstdio> 2 #include <cstring> 3 #include <cstdlib> 4 #include <iostream> 5 #include <algorithm> 6  7 using namespace std; 8  9 const int maxn = 200000 + 10;10 int a[maxn];11 struct node12 {13     int l, r, v;14 15 } va[maxn<<2];16 17 void build(int l, int r, int i)18 {19     va[i].l = l;20     va[i].r = r;21     int m = (l + r)/2;22     if(l == r) {23         va[i].v = a[l];24         return ;25     }26     build(l, m, i<<1);27     build(m+1, r, i<<1|1);28     va[i].v = max(va[i<<1].v, va[i<<1|1].v);29 }30 31 void Update(int id, int num, int i)32 {33     if(va[i].l == va[i].r) {34         va[i].v = num;35         return ;36     }37     else {38         if(id <= va[i<<1].r) Update(id, num, i<<1);39         else Update(id, num, i<<1|1);40     }41     va[i].v = max(va[i<<1].v, va[i<<1|1].v);42 }43 44 int Quary(int l, int r, int i)45 {46     int m = (va[i].l + va[i].r)/2;47     if(l == va[i].l && r == va[i].r) {48         return va[i].v;49     }50     if(r <= m) return Quary(l, r, i<<1);51     else if(l > m) return Quary(l, r, i<<1|1);52     else return max(Quary(l, m, i<<1), Quary(m+1, r, i<<1|1));53 }54 int main()55 {56     //freopen("test.in", "r", stdin);57     char s[5];58     int N, M, x, y;59     while(scanf("%d%d", &N, &M) != EOF) {60         for(int i = 1; i <= N; i++) {61             scanf("%d", &a[i]);62         }63         build(1, N, 1);64         while(M--) {65             scanf("%s %d %d", s, &x, &y);66             if(s[0] == ‘Q‘) printf("%d\n", Quary(x, y, 1));67             else Update(x, y, 1);68         }69     }70     return 0;71 }

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