USACO部分试题答案1.2.4；1.2.5；1.3.1

package Karl.Water;

/*
LANG: JAVA
PROG: dualpal
*/


import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.StringTokenizer;

public class dualpal {
	public static void main(String[] args) throws IOException {
		BufferedReader in = new BufferedReader(new FileReader("dualpal.in"));
		PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter("dualpal.out")), true);
		StringTokenizer st = new StringTokenizer(in.readLine());
		int N = Integer.parseInt(st.nextToken());
		int S = Integer.parseInt(st.nextToken());
		do {
			if (dualPal(++S)) {
				out.println(S);
				if (--N == 0)
					break;
			}
		} while (S != Integer.MAX_VALUE);
		System.exit(0);
	}

	private static char digitToChar(int digit) {
		return (char) (digit + '0');
	}

	private static boolean dualPal(int num) {
		int count = 0;
		int base = 2;
		do {
			if (isPal(toBaseForm(num, base))) {
				if (++count >= 2)
					return true;
			}
		} while (++base <= 10);
		return false;
	}

	private static String toBaseForm(int num, int base) {
		StringBuilder sb = new StringBuilder();
		do {
			char curChar = digitToChar(num % base);
			sb.append(curChar);
		} while ((num /= base) != 0);
		sb.reverse();
		return sb.toString();
	}

	private static boolean isPal(String s) {
		int low = 0, high = s.length() - 1;
		while (low < high) {
			if (s.charAt(low) != s.charAt(high))
				return false;
			low++;
			high--;
		}
		return true;
	}
}

第二题
package Karl.Water;

/*
LANG: JAVA
TASK: palsquare
*/

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;

public class palsquare {
	static char[] a ={'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F','G','H','I','J','K'};
	public static boolean judgehuiwen(String s){
		for(int i=0;i<s.length()/2;i++){
			if(s.charAt(i)!=s.charAt(s.length()-1-i))
				return false;
		}
		return true;
	}
	public static String judge(Integer i,Integer j){
		if(i/j==0){
			return String.valueOf(a[i%j]);
		}else{
			return judge(i/j,j)+String.valueOf(a[i%j]);
		}
	}
	public static void judgepingfang(int j) throws IOException{
		PrintWriter pw = new PrintWriter (new FileWriter("palsquare.out"));
		for(int i=1;i<=300;i++){
			if(judgehuiwen(judge(i*i,j)))
				pw.println(judge(i,j)+" "+judge(i*i,j));
		}
		pw.close();
	}
	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new FileReader("palsquare.in"));
		judgepingfang(Integer.parseInt(br.readLine()));
		br.close();
	}
}
第三题：
package Karl.Water;

/*
LANG:JAVA
TASK:milk
*/

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.StringTokenizer;

public class milk {
	public static void quick_sort(int[][] arr,int begin,int end){
		for(int x=0;x<arr.length-1;x++){
			for(int y=0;y<arr.length-x-1;y++){
				if(arr[y][0]>arr[y+1][0]){
					int temp=0;
					int temper=0;
					temp=arr[y][0];
					temper=arr[y][1];
					arr[y][0]=arr[y+1][0];
					arr[y][1]=arr[y+1][1];
					arr[y+1][0]=temp;
					arr[y+1][1]=temper;
				}
			}
		}
	}
	public static void fun(int[][] a,int needNum,int lineNum) throws IOException {
		PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter("milk.out")), true);
		int k = 0;
		int money = 0;
		if(a.length==0){
			out.println(0);
		}
		for(int i=0;i<lineNum;i++){
			k = k + a[i][1];
			money = money + a[i][0]*a[i][1];
			if(k==needNum){
				out.println(money);
				break;
			}
			if(k>needNum){
				money=(a[i][1]-(k-needNum))*a[i][0]+(money-a[i][0]*a[i][1]);
				out.println(money);
				break;
			}
		}
		out.close();
	}
	public static void agg() throws IOException {
		BufferedReader in = new BufferedReader(new FileReader("milk.in"));
		StringTokenizer st = new StringTokenizer(in.readLine());
		int need = Integer.parseInt(st.nextToken());
		int farmerNum = Integer.parseInt(st.nextToken());
		int[][] a = new int[farmerNum][2];
		for(int i=0;i<farmerNum;i++){
			st = new StringTokenizer(in.readLine());
			a[i][0] = Integer.parseInt(st.nextToken());
			a[i][1] = Integer.parseInt(st.nextToken());
		}
		quick_sort(a,0,farmerNum-1);
		fun(a,need,farmerNum);
	}
	public static void main(String[] args) throws IOException {
		agg();
	}
}