本来打完就想写的，，奈何舍友要睡了，我开个台灯感觉怪怪的，就没写。
A题竟然一开始wa了。。。后来发现对于c和a还有c和b的关系没有判断，，丢掉了很多罚时。
B题我的方法是 计算 sum，然后 分别统计 2、3、4的个数，一个一个试，具体看代码(前面快速io有点长见谅
package R491; import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.util.StringTokenizer; public class Main2 {
static BufferedReader in=new BufferedReader(new InputStreamReader(System.in));
static StringTokenizer tok;
static boolean hasNext()
{
while(tok==null||!tok.hasMoreTokens())
try{
tok=new StringTokenizer(in.readLine());
}
catch(Exception e){
return false;
}
return true;
}
static String next()
{
hasNext();
return tok.nextToken();
}
static long nextLong()
{
return Long.parseLong(next());
}
static int nextInt()
{
return Integer.parseInt(next());
}
static PrintWriter out=new PrintWriter(new OutputStreamWriter(System.out)); public static void main(String[] args) {
int n = nextInt();
int a[] = new int[n];
int b[] = new int[8];
int sum = 0;
for(int i=0;i<n;i++){
a[i] = nextInt();
b[a[i]]++;
sum+=a[i];
}
int num = 0;
while (sum<4.5*n){
if (b[2]>0){
sum+=3;
b[2]--;
num++;
}else if (b[3]>0){
sum+=2;
b[3]--;
num++;
}else if (b[4]>0){
sum+=1;
b[4]--;
num++;
}
}
out.print(num);
out.flush();
}
}
C 一开始还以为可能有点意思，然后二分板子就出来了，没啥可说的，中间竟然wa了一发，，很玄学， ，判断时 如果 把 num1>=num2 写成 num1>=(double)n/2 就会wa。。。
package R491; import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.util.StringTokenizer; public class Main3 {
static BufferedReader in=new BufferedReader(new InputStreamReader(System.in));
static StringTokenizer tok;
static boolean hasNext()
{
while(tok==null||!tok.hasMoreTokens())
try{
tok=new StringTokenizer(in.readLine());
}
catch(Exception e){
return false;
}
return true;
}
static String next()
{
hasNext();
return tok.nextToken();
}
static long nextLong()
{
return Long.parseLong(next());
}
static int nextInt()
{
return Integer.parseInt(next());
}
static PrintWriter out=new PrintWriter(new OutputStreamWriter(System.out)); static long n;
public static void main(String[] args) {
n = nextLong();
long l = 1;
long r = n;
while (l<=r){
long mid=(l+r)/2;
if (caneat(mid)){
r=mid-1;
}else {
l=mid+1;
}
}
out.print(l);
out.flush();
}
public static boolean caneat(long k){
long num=0;
long num2 = 0;
long temp = n;
while (temp>0){
if (temp<k){
num+=temp;
break;
}
num+=k;
temp-=k;
num2+=(temp/10);
temp-=temp/10;
}
if (num>=num2){
return true;
}else {
return false;
}
}
}
D题就很和蔼可亲了，竟然只有两行，直接暴力，我的方法是 umm懒得说看代码吧
package R491; import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.util.StringTokenizer; public class Main4 {
static BufferedReader in=new BufferedReader(new InputStreamReader(System.in));
static StringTokenizer tok;
static boolean hasNext()
{
while(tok==null||!tok.hasMoreTokens())
try{
tok=new StringTokenizer(in.readLine());
}
catch(Exception e){
return false;
}
return true;
}
static String next()
{
hasNext();
return tok.nextToken();
}
static long nextLong()
{
return Long.parseLong(next());
}
static int nextInt()
{
return Integer.parseInt(next());
}
static PrintWriter out=new PrintWriter(new OutputStreamWriter(System.out)); public static void main(String[] args) {
String s[] = new String[2];
for(int i=0;i<2;i++){
s[i] = next();
}
if (s[0].length()==1){
out.print(0);
out.flush();
return;
}
char ch1[] = s[0].toCharArray();
char ch2[] = s[1].toCharArray();
int ans = 0;
for(int i=0;i<ch1.length;i++){
if (ch1[i]=='0'&&ch2[i]=='0'){
if (i==0){
if (ch1[i+1]=='0'){
ans++;
ch1[i+1]='X';
ch1[i]=ch2[i]='X';
}else if (ch2[i+1]=='0'){
ans++;
ch2[i+1]='X';
ch1[i]=ch2[i]='X';
}
}else if (i<ch1.length-1){
if (ch1[i-1]=='0'){
ans++;
ch1[i-1]='X';
ch1[i]=ch2[i]='X';
}else if (ch2[i-1]=='0'){
ans++;
ch2[i-1]='X';
ch1[i]=ch2[i]='X';
}else if (ch1[i+1]=='0'){
ans++;
ch1[i+1]='X';
ch1[i]=ch2[i]='X';
}else if (ch2[i+1]=='0'){
ans++;
ch2[i+1]='X';
ch1[i]=ch2[i]='X';
}
}else if (i== ch1.length-1) {
if (ch1[i - 1] == '0') {
ans++;
ch1[i - 1] = 'X';
ch1[i] = ch2[i] = 'X';
} else if (ch2[i - 1] == '0') {
ans++;
ch2[i - 1] = 'X';
ch1[i] = ch2[i] = 'X';
}
}
}
}
out.print(ans);
out.flush();
}
}
E 啊哈哈哈哈，尴尬而不失礼貌的微笑，因为我太弱了又很垃圾还是一个数学白痴所以我没写出来。。。
F学长都没写。。。学长51分钟过掉ABCDE好像就开始挂机了，发现F有点难就睡觉去了，然后D题掉了，囍。
近期：补一下排列组合，抓紧学个tarjan把前天的E题补掉。(对不起是我太弱了不会tarjan
rating:1548
忽然发现今晚还有一场，我可能要1600+了欸嘿嘿嘿。