c/c++语言开发共享洛谷P4717 【模板】快速沃尔什变换(FWT)

题意

题目链接

sol

背板子背板子

#include<bits/stdc++.h> using namespace std; const int maxn = (1 << 17) + 10, mod = 998244353, inv2 = 499122177; inline int read() {     char c = getchar(); int x = 0, f = 1;     while(c < '0' || c > '9') {if(c == '-') f = -1; c = getchar();}     while(c >= '0' && c <= '9') x = x * 10 + c - '0', c = getchar();     return x * f; } int n, a[maxn], b[maxn], c[maxn]; int add(int x, int y) {     if(x + y < 0) return x + y + mod;     return x + y >= mod ? x + y - mod : x + y; } int mul(int x, int y) {     return 1ll * x * y % mod; } void fwtor(int *a, int opt) {     for(int mid = 1; mid < n; mid <<= 1)          for(int r = mid << 1, j = 0; j < n; j += r)             for(int k = 0; k < mid; k++)                  if(opt == 1) a[j + k + mid] = add(a[j + k], a[j + k + mid]);                 else a[j + k + mid] = add(a[j + k + mid], -a[j + k]); } void fwtand(int *a, int opt) {     for(int mid = 1; mid < n; mid <<= 1)          for(int r = mid << 1, j = 0; j < n; j += r)             for(int k = 0; k < mid; k++)                  if(opt == 1) a[j + k] = add(a[j + k], a[j + k + mid]);                 else a[j + k] = add(a[j + k], -a[j + k + mid]); } void fwtxor(int *a, int opt) {     for(int mid = 1; mid < n; mid <<= 1)          for(int r = mid << 1, j = 0; j < n; j += r)             for(int k = 0; k < mid; k++) {                 int x = a[j + k], y = a[j + k + mid];                 if(opt == 1) a[j + k] = add(x, y), a[j + k + mid] = add(x, -y);                 else a[j + k] = mul(add(x, y), inv2), a[j + k + mid] = mul(add(x, -y), inv2);                            }  } int main() {     n = 1 << (read());     for(int i = 0; i < n; i++) a[i] = read();     for(int i = 0; i < n; i++) b[i] = read();     fwtor(a, 1); fwtor(b, 1);     for(int i = 0; i < n; i++) c[i] = mul(a[i], b[i]);     fwtor(c, -1); fwtor(a, -1); fwtor(b, -1);     for(int i = 0; i < n; i++) printf("%d ", c[i]); puts("");     fwtand(a, 1); fwtand(b, 1);     for(int i = 0; i < n; i++) c[i] = mul(a[i], b[i]);     fwtand(c, -1); fwtand(a, -1); fwtand(b, -1);         for(int i = 0; i < n; i++) printf("%d ", c[i]); puts("");     fwtxor(a, 1); fwtxor(b, 1);     for(int i = 0; i < n; i++) c[i] = mul(a[i], b[i]);     fwtxor(c, -1); fwtxor(a, -1); fwtxor(b, -1);         for(int i = 0; i < n; i++) printf("%d ", c[i]);     return 0; }