題目大意：有一個長度為$n$的$01$串，兩個操作：

$1\;l\;r：$把區間$[l,r]$翻轉（$0->1,1->0$）

$2\;p：$求第$p$位是什么

題解：維護前綴異或和，樹狀數組即可

卡點：無

?

C++ Code：

#include <cstdio> #include <cctype>namespace std {struct istream { #define M (1 << 24 | 3)char buf[M], *ch = buf - 1;inline istream() { #ifndef ONLINE_JUDGEfreopen("input.txt", "r", stdin); #endiffread(buf, 1, M, stdin);}inline istream& operator >> (int &x) {while (isspace(*++ch));for (x = *ch & 15; isdigit(*++ch); ) x = x * 10 + (*ch & 15);return *this;} #undef M} cin;struct ostream { #define M (1 << 24 | 3)char buf[M], *ch = buf - 1;int w;inline ostream& operator << (int x) {if (!x) {*++ch = '0';return *this;}for (w = 1; w <= x; w *= 10);for (w /= 10; w; w /= 10) *++ch = (x / w) ^ 48, x %= w;return *this;}inline ostream& operator << (const char x) {*++ch = x; return *this;}inline ostream& operator << (const char *x) {while (*x) *this << *x++;return *this;}inline ~ostream() { #ifndef ONLINE_JUDGEfreopen("output.txt", "w", stdout); #endiffwrite(buf, 1, ch - buf + 1, stdout);} #undef M} cout; }#define maxn 100010int n, m; namespace BIT {int Tr[maxn], res;inline void add(int p) {for (; p <= n; p += p & -p) Tr[p] ^= 1;}inline int ask(int p) {for (res = 0; p; p &= p - 1) res ^= Tr[p]; return res;} }int main() {std::cin >> n >> m;while (m --> 0) {int op, l, r;std::cin >> op >> l;if (op == 1) {std::cin >> r;BIT::add(l), BIT::add(r + 1);} else std::cout << BIT::ask(l) << '\n';}return 0; }

　　

轉載于:https://www.cnblogs.com/Memory-of-winter/p/10127483.html

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