牛客练习赛24
AK的感觉真好233
T1
$\large m*(m-1)^{n-1}$
#include <iostream> #include <cstdio> #include <cstring> #include <cmath> #include <algorithm> #include <queue> using namespace std; #define reg register #define int long long inline int read() { int res=0;char c=getchar();bool f=0; while(!isdigit(c)) {if(c=='-')f=1;c=getchar();} while(isdigit(c))res=(res<<3)+(res<<1)+(c^48),c=getchar(); return f?-res:res; } #define mod 1000000007 int n, m; inline int ksm(int x, int y) { int res = 1; while(y) { if (y & 1) res = res * x % mod; x = x * x % mod; y >>= 1; } return res; } signed main() { n = read(), m = read(); printf ("%lld\n", (ksm(m - 1, n - 1) * m) % mod); return 0; }
T2
就是dfs一遍求出以1为根的每个子树的siz，然后答案就是1的所有儿子的siz的最大值。
#include <iostream> #include <cstdio> #include <cstring> #include <cmath> #include <algorithm> #include <queue> using namespace std; #define reg register inline int read() { int res=0;char c=getchar();bool f=0; while(!isdigit(c)) {if(c=='-')f=1;c=getchar();} while(isdigit(c))res=(res<<3)+(res<<1)+(c^48),c=getchar(); return f?-res:res; } int n; struct edge { int nxt, to; }ed[1000005*2]; int head[1000005], cnt; inline void add(int x, int y) { ed[++cnt] = (edge){head[x], y}; head[x] = cnt; } int siz[1000005]; int deg[1000005]; void dfs(int x, int fa) { siz[x] = 1; for (reg int i = head[x] ; i ; i = ed[i].nxt) { int to = ed[i].to; if (to == fa) continue; dfs(to, x); siz[x] += siz[to]; } } int ans; int main() { n = read(); for (reg int i = 1 ; i < n ; i ++) { int x = read(), y = read(); add(x, y), add(y, x); } dfs(1, 0); for (reg int i = head[1] ; i ; i = ed[i].nxt) ans = max(ans, siz[ed[i].to]); cout<<ans<<endl; return 0; }
T3
线段树上二分不想说了。
#include <iostream> #include <cstdio> #include <cstring> #include <cmath> #include <algorithm> #include <queue> using namespace std; #define reg register inline int read() { int res=0;char c=getchar();bool f=0; while(!isdigit(c)) {if(c=='-')f=1;c=getchar();} while(isdigit(c))res=(res<<3)+(res<<1)+(c^48),c=getchar(); return f?-res:res; } #define N 1000005 int n, m; int n1, n2; char a[N]; int ans; struct Segment { int num1, num2; }t[N<<2]; #define ls(o) o << 1 #define rs(o) o << 1 | 1 #define s1(o) t[o].num1 #define s2(o) t[o].num2 inline void update(int o) { s1(o) = s1(ls(o)) + s1(rs(o)); s2(o) = s2(ls(o)) + s2(rs(o)); } void Build(int l, int r, int o) { if (l == r) { if (a[l] == 'R') s1(o) = 1, n1++; else s2(o) = 1, n2++; return ; } int mid = l + r >> 1; Build(l, mid, ls(o)); Build(mid + 1, r, rs(o)); update(o); } void query1(int l, int r, int o, int kt) { if (l == r) { ans = l; return ; } int mid = l + r >> 1; if (s1(ls(o)) >= kt) query1(l, mid, ls(o), kt); else query1(mid + 1, r, rs(o), kt - s1(ls(o))); } void query2(int l, int r, int o, int kt) { if (l == r) { ans = l; return ; } int mid = l + r >> 1; if (s2(ls(o)) >= kt) query2(l, mid, ls(o), kt); else query2(mid + 1, r, rs(o), kt - s2(ls(o))); } int main() { n = read(), m = read(); for (register int i = 1 ; i <= n ; i ++) cin >> a[i]; Build(1, n, 1); while(m--) { char typ; int k; ans = 0; cin >> typ; k = read(); if (typ == 'R') { if (n1 < k) {puts("-1");continue;} query1(1, n, 1, k); printf("%d\n", ans); } else { if (n2 < k) {puts("-1");continue;} query2(1, n, 1, k); printf("%d\n", ans); } } return 0; }
T4
dfs一遍就行。
#include <iostream> #include <cstdio> #include <cstring> #include <cmath> #include <algorithm> #include <queue> using namespace std; #define reg register inline int read() { int res=0;char c=getchar();bool f=0; while(!isdigit(c)) {if(c=='-')f=1;c=getchar();} while(isdigit(c))res=(res<<3)+(res<<1)+(c^48),c=getchar(); return f?-res:res; } #define N 50005 int n; struct edge { int nxt, to, val; }ed[N*2]; int head[N], cnt; int deg[N]; inline void add(int x, int y, int z) { ed[++cnt] = (edge){head[x], y, z}; head[x] = cnt; } int rt, ans; void dfs(int x, int fa, int sum) { ans = max(ans, sum); for (reg int i = head[x] ; i ; i = ed[i].nxt) { int to = ed[i].to; if (to == fa) continue; dfs(to, x, sum + ed[i].val); } } int main() { n = read(); for (reg int i = 1 ; i < n ; i ++) { int x = read(), y = read(), z = read(); add(y, x, z); deg[x]++; } for (reg int i = 1 ; i <= n ; i ++) if (deg[i] == 0) {rt = i;break;} dfs(rt, 0, 0); printf("%d\n", ans); return 0; }
T5
建边spfa
#include <iostream> #include <cstdio> #include <cstring> #include <cmath> #include <algorithm> #include <queue> using namespace std; #define reg register inline int read() { int res=0;char c=getchar();bool f=0; while(!isdigit(c)) {if(c=='-')f=1;c=getchar();} while(isdigit(c))res=(res<<3)+(res<<1)+(c^48),c=getchar(); return f?-res:res; } #define N 500 int n, m; struct edge { int nxt, to, val; }ed[N*2]; int head[N], cnt; inline void add(int x, int y, int z) { ed[++cnt] = (edge){head[x], y, z}; head[x] = cnt; } int dis[N]; bool ex[N]; inline void spfa() { memset(dis, 0x3f, sizeof dis); queue <int> q; dis[0] = 0; q.push(0); while(!q.empty()) { int x = q.front();q.pop(); ex[x] = 0; for (reg int i = head[x] ; i ; i = ed[i].nxt) { int to = ed[i].to; if (dis[to] > dis[x] + 1) { dis[to] = dis[x] + 1; if (!ex[to]) ex[to] = 1, q.push(to); } } } } int main() { m = read(), n = read(); for (reg int i = 0 ; i <= m ; i ++) add(i, i + 1, 1), add(i + 1, i, 1); for (reg int i = 1 ; i <= n ; i ++) { int x = read(), y = read(); add(x, y, 1); } spfa(); // for (int i = 1 ; i <= m ; i ++) printf("%d %d\n", i, dis[i]); printf("%d\n", dis[m]); return 0; }
T6
直接n^2做， 虽然不知道为什么能过。
%:pragma GCC optimize(3) %:pragma GCC optimize("Ofast") %:pragma GCC optimize("inline") %:pragma GCC optimize("-fgcse") %:pragma GCC optimize("-fgcse-lm") %:pragma GCC optimize("-fipa-sra") %:pragma GCC optimize("-ftree-pre") %:pragma GCC optimize("-ftree-vrp") %:pragma GCC optimize("-fpeephole2") %:pragma GCC optimize("-ffast-math") %:pragma GCC optimize("-fsched-spec") %:pragma GCC optimize("unroll-loops") %:pragma GCC optimize("-falign-jumps") %:pragma GCC optimize("-falign-loops") %:pragma GCC optimize("-falign-labels") %:pragma GCC optimize("-fdevirtualize") %:pragma GCC optimize("-fcaller-saves") %:pragma GCC optimize("-fcrossjumping") %:pragma GCC optimize("-fthread-jumps") %:pragma GCC optimize("-funroll-loops") %:pragma GCC optimize("-fwhole-program") %:pragma GCC optimize("-freorder-blocks") %:pragma GCC optimize("-fschedule-insns") %:pragma GCC optimize("inline-functions") %:pragma GCC optimize("-ftree-tail-merge") %:pragma GCC optimize("-fschedule-insns2") %:pragma GCC optimize("-fstrict-aliasing") %:pragma GCC optimize("-fstrict-overflow") %:pragma GCC optimize("-falign-functions") %:pragma GCC optimize("-fcse-skip-blocks") %:pragma GCC optimize("-fcse-follow-jumps") %:pragma GCC optimize("-fsched-interblock") %:pragma GCC optimize("-fpartial-inlining") %:pragma GCC optimize("no-stack-protector") %:pragma GCC optimize("-freorder-functions") %:pragma GCC optimize("-findirect-inlining") %:pragma GCC optimize("-fhoist-adjacent-loads") %:pragma GCC optimize("-frerun-cse-after-loop") %:pragma GCC optimize("inline-small-functions") %:pragma GCC optimize("-finline-small-functions") %:pragma GCC optimize("-ftree-switch-conversion") %:pragma GCC optimize("-foptimize-sibling-calls") %:pragma GCC optimize("-fexpensive-optimizations") %:pragma GCC optimize("-funsafe-loop-optimizations") %:pragma GCC optimize("inline-functions-called-once") %:pragma GCC optimize("-fdelete-null-pointer-checks") #include <iostream> #include <cstdio> #include <cstring> #include <cmath> #include <algorithm> #include <queue> using namespace std; #define reg register inline int read() { int res=0;char c=getchar();bool f=0; while(!isdigit(c)) {if(c=='-')f=1;c=getchar();} while(isdigit(c))res=(res<<3)+(res<<1)+(c^48),c=getchar(); return f?-res:res; } #define mod 19260817 int n, m; int f[50005]; int main() { n = read(), m = read(); f[0] = 1; for (reg int i = 1 ; i <= n ; i ++) { int v = read(); for (reg int j = v ; j <= m ; j ++) { f[j] = f[j-v] + f[j]; if (f[j] >= mod) f[j] -= mod; } } int ans = 0; for (reg int i = 1 ; i <= m ; i ++) { ans += f[i]; if (ans >= mod) ans -= mod; } printf("%d\n", ans); return 0; }
