5 6
1 2 3 4 5
Q 1 5
U 3 6
Q 3 4
Q 4 5
U 2 9
Q 1 5

5
6
5
9

HintHuge input,the C function scanf() will work better than cin 

這會兒在看線段樹，做個題試試

線段樹功能:update:單點替換 query:區間最值

AC代碼：

#include 
#include 
#include 
using namespace std;

const int maxn = 200005;
int MAX[maxn<<2];

void pushup(int rt) {
	MAX[rt] = max(MAX[rt << 1], MAX[rt << 1 | 1]);
}

void build(int l, int r, int rt) {
	if(l == r) {
		scanf("%d", &MAX[rt]);
		return ;
	}
	int m = (l + r) >> 1;
	build(l, m, rt << 1);
	build(m + 1, r, rt << 1 | 1);
	pushup(rt);
}

void update(int p, int sc, int l, int r, int rt) {
	if(l == r) {
		MAX[rt] = sc;
		return; 
	}
	int m = (l + r) >> 1;
	if(p <= m) update(p, sc, l, m, rt << 1);
	else update(p, sc, m + 1, r, rt << 1 | 1);
	pushup(rt);
}

int query(int L, int R, int l, int r, int rt) {
	if(L <= l && r <= R) {
		return MAX[rt];	
	}
	int m = (l + r) >> 1;
	int ret = 0;
	if(L <= m) ret = max(ret, query(L, R, l, m, rt << 1));
	if(R > m) ret = max(ret, query(L, R, m + 1, r, rt << 1 | 1));
	return ret;
}

int main() {
	int n, m;
	while(scanf("%d %d", &n, &m) != EOF) {
		build(1, n, 1);
		while(m--) {
			char ord[5];
			int a, b;
			scanf("%s %d %d", ord, &a, &b);
			if(ord[0] == 'Q') printf("%d\n", query(a, b, 1, n, 1));
			else update(a, b, 1, n, 1);
		}
	}
	return 0;
}