[洛谷P3293][SCOI2016]美味

题目大意：有$n$个数，$m$个询问，每个询问给你$b\;x\;l\;r$表示在区间$[l,r]$中寻找一个数$p$，使得$b\oplus(a+x)$最大

题解：主席树，每一位贪心，若$b$第$i$位为$1$，就询问$[l,r]$中是否有数在$[ans-x,ans-x-1+2^i]$范围内（$ans$为前几位贪心出来的最优的$a+x$）

卡点：无

C++ Code：

#include <cstdio>
#include <cctype>
namespace R {
	int x, ch;
	inline int read() {
		ch = getchar();
		while (isspace(ch)) ch = getchar();
		for (x = ch & 15, ch = getchar(); isdigit(ch); ch = getchar()) x = x * 10 + (ch & 15);
		return x;
	}
}
using R::read;

#define maxn 200010
#define M 17
#define N (maxn * (M + 2))
const int maxl = 0, maxr = 99999;

namespace SgT {
	int V[N], lc[N], rc[N], idx;
	
	void insert(int &rt, int l, int r, int num) {
		lc[++idx] = lc[rt], rc[idx] = rc[rt], V[idx] = V[rt] + 1, rt = idx;
		if (l == r) return ;
		int mid = l + r >> 1;
		if (num <= mid) insert(lc[rt], l, mid, num);
		else insert(rc[rt], mid + 1, r, num);
	}
	bool query(int rtL, int rtR, int l, int r, int L, int R) {
		if (R < l || L > r) return false;
		if (L <= l && R >= r) return V[rtR] - V[rtL];
		int mid = l + r >> 1;
		if (L <= mid && query(lc[rtL], lc[rtR], l, mid, L, R)) return true;
		if (R > mid && query(rc[rtL], rc[rtR], mid + 1, r, L, R)) return true;
		return false;
	}
}

int n, m, rt[maxn];
int main() {
	n = read(), m = read();
	for (int i = 1; i <= n; i++) {
		SgT::insert(rt[i] = rt[i - 1], maxl, maxr, read());
	}
	while (m --> 0) {
		int b = read(), x = read(), l = read(), r = read();
		int ans = 0;
		for (int i = M; ~i; i--) {
			if (b >> i & 1) {
				if (!SgT::query(rt[l - 1], rt[r], maxl, maxr, ans - x, ans - x - 1 + (1 << i))) ans += 1 << i;
			} else {
				if (SgT::query(rt[l - 1], rt[r], maxl, maxr, ans - x + (1 << i), ans - x - 1 + (2 << i))) ans += 1 << i;
			}
		}
		printf("%d\n", ans ^ b);
	}
	return 0;
}