1. 小于N的质数数量
import java.util.Scanner;
/**
* 计算小于N的质数数量
* @author Turing
*
*/
public class Main4 {
public static void main( String[] args ) {
Scanner sc = new Scanner(System.in);
int [] arr = new int[100];
int num = 0;
while(sc.hasNextLine()){
String str = sc.nextLine().trim();
if(str.equals("")){
break;
}else{
arr[num++] = Integer.valueOf(str);
}
}
for (int i = 0; i < num; i++) {
System.out.println(primesNum(arr[i]));
}
}
public static int primesNum(int n){
boolean[] num = new boolean[n];
int number = 0;
for (int i = 2; i < n; i++) {
if(!num[i]){
number++;
for (int j = 2; i*j < n; j++) {
num[i*j]=true;
}
}
}
return number;
}
}
2. 逆时针二维数组 60%
import java.util.Scanner;
/**
* 逆时针打印矩阵
* @author Turing
*
*/
public class Main3 {
public static void main( String[] args ) {
Scanner sc = new Scanner(System.in);
String[] results = new String[100];
int index = 0;
while(sc.hasNextLine()){
String str = sc.nextLine().trim();
if(str.equals("")){
break;
}else{
String[] strs = str.split(" ");
int M = Integer.valueOf(strs[0]);
int N = Integer.valueOf(strs[1]);
int [][] matrix = new int [M][N];
int value = 1;
for (int i = 0; i < M; i++) {
for (int j = 0; j < N; j++) {
matrix[i][j] = value;
value++;
}
}
results[index++] = spiral(matrix, M, N);
}
}
for (int i = 0; i < index; i++) {
System.out.println(results[i]);
}
}
public static String spiral(int[][] matrix,int M,int N){
String result = "";
if(M!=0){
int row1 = 0;
int row2 = M -1;
int col1 = 0;
int col2 = N-1;
while(row1<=row2 && col1<=col2){
for (int i = col2; i >=col1; i--) {
result += matrix[row1][i] +" ";
}
for (int i = row1+1; i <=row2; i++) {
result += matrix[i][col1] +" ";
}
if(row1<row2 && col1<col2){
for (int i = col1+1; i < col2; i++) {
result += matrix[row2][i] +" ";
}
for (int i = row2; i > row1; i--) {
result += matrix[i][col2] +" ";
}
}
row1++;
row2--;
col1++;
col2--;
}
}
return result.trim();
}
}
3. 判断a+b>c
import java.util.Scanner;
/**
* a + b > C
* int64 int64 int64
* [-2^36,-2^63-1]
* @author Turing
*
*/
public class Main2 {
public static void main( String[] args ) {
Scanner sc = new Scanner(System.in);
boolean[] results = new boolean[100];
int index = 0;
while(sc.hasNextLine()){
String str = sc.nextLine().trim();
if(str.equals("")){
break;
}else{
String[] strs = str.split(" ");
long a = Long.valueOf(strs[0]);
long b = Long.valueOf(strs[1]);
long c = Long.valueOf(strs[2]);
results[index++] = abc(a, b, c);
}
}
for (int i = 0; i < index; i++) {
System.out.println(results[i]);
}
}
public static boolean abc(long a, long b, long c){
if(a>0 && b>0 && a+b<0){
return true;
}
if(a<0 && b<0 && a+b>0){
return false;
}
return a+b>c?true:false;
}
}