P163、面试题29：数组中出现次数超过一半的数字

package com.yyq;
/**
 * Created by gao on 15-10-23.
 */
public class MoreThanHalfNumber {
    public static boolean g_bInputInvalid = false;
    public static boolean checkInvalidArray(int[] numbers, int length) {
        g_bInputInvalid = false;
        if (numbers == null || length <= 0) {
            System.out.printf("Numbers is null! Invalid Parameters.");
            g_bInputInvalid = true;
        }
        return g_bInputInvalid;
    }
    public static boolean checkMoreThanHalf(int[] numbers, int length, int number) {
        int times = 0;
        for (int i = 0; i < length; i++) {
            if (number == numbers[i])
                times++;
        }
        boolean isMoreThanHalf = true;
        if (times * 2 <= length) {
            System.out.println("the number you find is not more than half.");
            isMoreThanHalf = false;
            g_bInputInvalid = true;
        }
        return isMoreThanHalf;
    }
    public static int Partition(int[] numbers, int length, int start, int end) {
        if (numbers == null || length <= 0 || start < 0 || end >= length) {
            System.out.printf("Invalid Parameters!");
            return -1;
        }
        int index = numbers[start];
        while (start < end) {
            while (start < end && numbers[end] >= index) end--;
            numbers[start] = numbers[end];
            while (start < end && numbers[start] <= index) start++;
            numbers[end] = numbers[start];
        }
        numbers[start] = index;
        return start;
    }
    //==================方法一:partition========================
    public static int moreThanHalfNum_solution1(int[] numbers, int length) {
        if (checkInvalidArray(numbers, length)) {
            return 0;
        }
        int middle = length >> 1;
        int start = 0;
        int end = length - 1;
        int index = Partition(numbers, length, start, end);
        while (index != middle) {
            if (index > middle) {
                end = index - 1;
                index = Partition(numbers, length, start, end);
            } else {
                start = index + 1;
                index = Partition(numbers, length, start, end);
            }
        }
        int result = numbers[middle];
        if (!checkMoreThanHalf(numbers, length, result)) {
            result = 0;
        }
        return result;
    }
    public static int moreThanHalfNum_solution2(int[] numbers, int length) {
        if (checkInvalidArray(numbers, length)) {
            return 0;
        }
        int result = numbers[0];
        int times = 1;
        for(int i = 1; i < length; i++){
            if (times == 0){
                result = numbers[i];
                times = 1;
            }
            else if(numbers[i] == result){
                times ++;
            }else{
                times--;
            }
        }
        if (!checkMoreThanHalf(numbers, length, result)) {
            result = 0;
        }
        return result;
    }
// ====================测试代码====================
    public static void Test(String testName, int[] numbers, int length, int expectedValue, boolean expectedFlag)
    {
        if(testName != null)
            System.out.println("\n"+testName+" begins: ");
        int[] copy = new int[length];
        for(int i = 0; i < length; ++i)
            copy[i] = numbers[i];
        System.out.printf("Test for solution1: ");
        int result = moreThanHalfNum_solution1(numbers, length);
        if(result == expectedValue && g_bInputInvalid == expectedFlag)
            System.out.println("Passed.");
        else
            System.out.println("Failed.");
        System.out.printf("Test for solution2: ");
        result = moreThanHalfNum_solution2(copy, length);
        if(result == expectedValue && g_bInputInvalid == expectedFlag)
            System.out.println("Passed.");
        else
            System.out.println("Failed.");
         copy = null;
    }
    // 存在出现次数超过数组长度一半的数字
    public static void Test1()
    {
        int numbers[] = {1, 2, 3, 2, 2, 2, 5, 4, 2};
        Test("Test1", numbers, numbers.length, 2, false);
    }
    // 不存在出现次数超过数组长度一半的数字
    public static void Test2()
    {
        int numbers[] = {1, 2, 3, 2, 4, 2, 5, 2, 3};
        Test("Test2", numbers, numbers.length, 0, true);
    }
    // 出现次数超过数组长度一半的数字都出现在数组的前半部分
    public static void Test3()
    {
        int numbers[] = {2, 2, 2, 2, 2, 1, 3, 4, 5};
        Test("Test3", numbers, numbers.length, 2, false);
    }
    // 出现次数超过数组长度一半的数字都出现在数组的后半部分
    public static void Test4()
    {
        int numbers[] = {1, 3, 4, 5, 2, 2, 2, 2, 2};
        Test("Test4", numbers, numbers.length, 2, false);
    }
    // 数组为1个元素
    public static void Test5()
    {
        int numbers[] = {1};
        Test("Test5", numbers, 1, 1, false);
    }
    // 输入空指针
    public static void Test6()
    {
        Test("Test6", null, 0, 0, true);
    }
    public static void main(String[] args)
    {
        Test1();
        Test2();
        Test3();
        Test4();
        Test5();
        Test6();
    }
}