Codeforces Round #613 (Div. 2) ABC 題解
阿新 • • 發佈：2020-09-11
A. Mezo Playing Zoma
題意：給你一個向右向左的指令，每個指令可以朝那個方向走一個單位，問你可以隨意選出子序列來走，那可能到達的點有多少個。
思路：從範圍上考慮就秒了。看最左和最右能到哪，然後加上原點就是所有可能的點數
view code
#include<iostream> #include<string> #include<algorithm> #include<cstdio> #include<cstring> #include<cmath> #include<map> #include <queue> #include<sstream> #include <stack> #include <set> #include <bitset> #include<vector> #define FAST ios::sync_with_stdio(false) #define abs(a) ((a)>=0?(a):-(a)) #define sz(x) ((int)(x).size()) #define all(x) (x).begin(),(x).end() #define mem(a,b) memset(a,b,sizeof(a)) #define max(a,b) ((a)>(b)?(a):(b)) #define min(a,b) ((a)<(b)?(a):(b)) #define rep(i,a,n) for(int i=a;i<=n;++i) #define per(i,n,a) for(int i=n;i>=a;--i) #define pb push_back #define mp make_pair #define fi first #define se second using namespace std; typedef long long ll; typedef pair<ll,ll> PII; const int maxn = 1e5+200; const int inf=0x3f3f3f3f; const double eps = 1e-7; const double pi=acos(-1.0); const int mod = 1e9+7; inline int lowbit(int x){return x&(-x);} ll gcd(ll a,ll b){return b?gcd(b,a%b):a;} void ex_gcd(ll a,ll b,ll &d,ll &x,ll &y){if(!b){d=a,x=1,y=0;}else{ex_gcd(b,a%b,d,y,x);y-=x*(a/b);}}//x=(x%(b/d)+(b/d))%(b/d); inline ll qpow(ll a,ll b,ll MOD=mod){ll res=1;a%=MOD;while(b>0){if(b&1)res=res*a%MOD;a=a*a%MOD;b>>=1;}return res;} inline ll inv(ll x,ll p){return qpow(x,p-2,p);} inline ll Jos(ll n,ll k,ll s=1){ll res=0;rep(i,1,n+1) res=(res+k)%i;return (res+s)%n;} inline ll read(){ ll f = 1; ll x = 0;char ch = getchar();while(ch>'9'||ch<'0') {if(ch=='-') f=-1; ch = getchar();}while(ch>='0'&&ch<='9') x = (x<<3) + (x<<1) + ch - '0', ch = getchar();return x*f; } int dir[4][2] = { {1,0}, {-1,0},{0,1},{0,-1} }; int main() { ll n = read(); string s; cin>>s; int l = 0, r = 0; for(int i=0; i<s.size(); i++) { if(s[i] == 'L') l++; else r++; } cout<<l+r+1<<endl; return 0; }
B. Just Eat It!
題意：給你一個序列，問你所有的和是否嚴格大於所有子段（不包含[1,n]這個）的和。
思路：其實就是模板題。求一個最大欄位和，同時記錄開始和結束位置。若存在一個滿足限制條件的最大欄位和dp[i]，則輸出NO，反之輸出YES。
view code
#include<iostream> #include<string> #include<algorithm> #include<cstdio> #include<cstring> #include<cmath> #include<map> #include <queue> #include<sstream> #include <stack> #include <set> #include <bitset> #include<vector> #define FAST ios::sync_with_stdio(false) #define abs(a) ((a)>=0?(a):-(a)) #define sz(x) ((int)(x).size()) #define all(x) (x).begin(),(x).end() #define mem(a,b) memset(a,b,sizeof(a)) #define max(a,b) ((a)>(b)?(a):(b)) #define min(a,b) ((a)<(b)?(a):(b)) #define rep(i,a,n) for(int i=a;i<=n;++i) #define per(i,n,a) for(int i=n;i>=a;--i) #define pb push_back #define mp make_pair #define fi first #define se second using namespace std; typedef long long ll; typedef pair<ll,ll> PII; const int maxn = 1e5+200; const int inf=0x3f3f3f3f; const double eps = 1e-7; const double pi=acos(-1.0); const int mod = 1e9+7; inline int lowbit(int x){return x&(-x);} ll gcd(ll a,ll b){return b?gcd(b,a%b):a;} void ex_gcd(ll a,ll b,ll &d,ll &x,ll &y){if(!b){d=a,x=1,y=0;}else{ex_gcd(b,a%b,d,y,x);y-=x*(a/b);}}//x=(x%(b/d)+(b/d))%(b/d); inline ll qpow(ll a,ll b,ll MOD=mod){ll res=1;a%=MOD;while(b>0){if(b&1)res=res*a%MOD;a=a*a%MOD;b>>=1;}return res;} inline ll inv(ll x,ll p){return qpow(x,p-2,p);} inline ll Jos(ll n,ll k,ll s=1){ll res=0;rep(i,1,n+1) res=(res+k)%i;return (res+s)%n;} inline ll read(){ ll f = 1; ll x = 0;char ch = getchar();while(ch>'9'||ch<'0') {if(ch=='-') f=-1; ch = getchar();}while(ch>='0'&&ch<='9') x = (x<<3) + (x<<1) + ch - '0', ch = getchar();return x*f; } int dir[4][2] = { {1,0}, {-1,0},{0,1},{0,-1} }; ll dp[maxn]; ll a[maxn]; ll s[maxn]; ll t[maxn]; int main() { int kase; cin>>kase; while(kase--) { ll n = read(); rep(i,0,n+1) dp[i] = 0; ll sum = 0; rep(i,1,n) a[i] = read(), sum += a[i]; ll st = 1, ed = 1; rep(i,1,n) { if(dp[i-1] + a[i] > a[i]) { dp[i] = dp[i-1] + a[i]; ed = i; s[i] = st, t[i] = ed; } else { dp[i] = a[i]; s[i] = t[i] = st = ed = i; } } int flag = 0; rep(i,1,n) if(dp[i]>=sum&&!(s[i]==1&&t[i]==n)) {flag=1; break;} puts(flag?"NO":"YES"); } return 0; }
C. Fadi and LCM
題意：問你找到一對(a,b),在滿足 LCM(a,b) = X 的情況下找出max(a,b)最小的一對。
由於\(LCM(a,b)\) = \(ab\over gcd(a,b)\)，所以當\(gcd(a,b)\)=1的時候能把ab限制的最小。所以只需要列舉一遍[1,\(\sqrt{x}\)]找到max(a,b)最小的對即可。
view code
#include<iostream> #include<string> #include<algorithm> #include<cstdio> #include<cstring> #include<cmath> #include<map> #include <queue> #include<sstream> #include <stack> #include <set> #include <bitset> #include<vector> #define FAST ios::sync_with_stdio(false) #define abs(a) ((a)>=0?(a):-(a)) #define sz(x) ((int)(x).size()) #define all(x) (x).begin(),(x).end() #define mem(a,b) memset(a,b,sizeof(a)) #define max(a,b) ((a)>(b)?(a):(b)) #define min(a,b) ((a)<(b)?(a):(b)) #define rep(i,a,n) for(int i=a;i<=n;++i) #define per(i,n,a) for(int i=n;i>=a;--i) #define pb push_back #define mp make_pair #define fi first #define se second using namespace std; typedef long long ll; typedef pair<ll,ll> PII; const int maxn = 1e5+200; const int inf=0x3f3f3f3f; const double eps = 1e-7; const double pi=acos(-1.0); const int mod = 1e9+7; inline int lowbit(int x){return x&(-x);} ll gcd(ll a,ll b){return b?gcd(b,a%b):a;} void ex_gcd(ll a,ll b,ll &d,ll &x,ll &y){if(!b){d=a,x=1,y=0;}else{ex_gcd(b,a%b,d,y,x);y-=x*(a/b);}}//x=(x%(b/d)+(b/d))%(b/d); inline ll qpow(ll a,ll b,ll MOD=mod){ll res=1;a%=MOD;while(b>0){if(b&1)res=res*a%MOD;a=a*a%MOD;b>>=1;}return res;} inline ll inv(ll x,ll p){return qpow(x,p-2,p);} inline ll Jos(ll n,ll k,ll s=1){ll res=0;rep(i,1,n+1) res=(res+k)%i;return (res+s)%n;} inline ll read(){ ll f = 1; ll x = 0;char ch = getchar();while(ch>'9'||ch<'0') {if(ch=='-') f=-1; ch = getchar();}while(ch>='0'&&ch<='9') x = (x<<3) + (x<<1) + ch - '0', ch = getchar();return x*f; } int dir[4][2] = { {1,0}, {-1,0},{0,1},{0,-1} }; int main() { ll x = read(); ll m = sqrt(x*1.0); ll ansx = x, ansy = 1; rep(i,1,m) { if(x%i) continue; ll j = x/i; if(gcd(i,j)==1&&max(i,j)<max(ansx,ansy)) ansx = i, ansy = j; } cout<<ansx<<' '<<ansy<<'\n'; return 0; }