JZ-C-29

剑指offer第二十九题：数组中出现次数超过一半的数字

//============================================================================
// Name        : JZ-C-29.cpp
// Author      : Laughing_Lz
// Version     :
// Copyright   : All Right Reserved
// Description : 数组中出现次数超过一半的数字
//============================================================================

#include <iostream>
#include "Array.h"
#include <stdio.h>
using namespace std;

bool g_bInputInvalid = false;
/**
 *检查数组是否合法
 */
bool CheckInvalidArray(int* numbers, int length) {
    g_bInputInvalid = false;
    if (numbers == NULL && length <= 0)
        g_bInputInvalid = true;

    return g_bInputInvalid;
}
/**
 * 检查数字出现次数是否大于数组长度一半
 */
bool CheckMoreThanHalf(int* numbers, int length, int number) {
    int times = 0;
    for (int i = 0; i < length; ++i) {
        if (numbers[i] == number)
            times++;
    }

    bool isMoreThanHalf = true;
    if (times * 2 <= length) {
        g_bInputInvalid = true;
        isMoreThanHalf = false;
    }

    return isMoreThanHalf;
}

// ====================方法1:分治法，参考快速排序====================
int MoreThanHalfNum_Solution1(int* numbers, int length) {
    if (CheckInvalidArray(numbers, length)) {
        return 0;
    }
    int middle = length >> 1; //右移1位
    int start = 0;
    int end = length - 1;
    int index = Partition(numbers, length, start, end);
    while (index != middle) {
        if (index < middle) {
            index = Partition(numbers, length, index + 1, end);
        } else {
            index = Partition(numbers, length, start, index - 1);
        }
    }
    int result = numbers[middle];
    if (!CheckMoreThanHalf(numbers, length, result)) {
        result = 0;
    }
    return result;
}
// ====================方法2:利用数字出现次数大于数组长度的一半====================
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 (result != numbers[i]) {
            times--;
        } else {
            times++;
        }
    }
    if (!CheckMoreThanHalf(numbers, length, result)) {
        result = 0;
    }
    return result;
}
// ====================测试代码====================
void Test(char* testName, int* numbers, int length, int expectedValue,
        bool expectedFlag) {
    if (testName != NULL)
        printf("%s begins: 
", testName);

    int* copy = new int[length];
    for (int i = 0; i < length; ++i)
        copy[i] = numbers[i];

    printf("Test for solution1: ");
    int result = MoreThanHalfNum_Solution1(numbers, length);
    if (result == expectedValue && g_bInputInvalid == expectedFlag)
        printf("Passed.
");
    else
        printf("Failed.
");

    printf("Test for solution2: ");
    result = MoreThanHalfNum_Solution2(copy, length);
    if (result == expectedValue && g_bInputInvalid == expectedFlag)
        printf("Passed.
");
    else
        printf("Failed.
");

    delete[] copy;
}

// 存在出现次数超过数组长度一半的数字
void Test1() {
    int numbers[] = { 1, 2, 3, 2, 2, 2, 5, 4, 2 };
    Test("Test1", numbers, sizeof(numbers) / sizeof(int), 2, false);
}

// 不存在出现次数超过数组长度一半的数字
void Test2() {
    int numbers[] = { 1, 2, 3, 2, 4, 2, 5, 2, 3 };
    Test("Test2", numbers, sizeof(numbers) / sizeof(int), 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
void Test3() {
    int numbers[] = { 2, 2, 2, 2, 2, 1, 3, 4, 5 };
    Test("Test3", numbers, sizeof(numbers) / sizeof(int), 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
void Test4() {
    int numbers[] = { 1, 3, 4, 5, 2, 2, 2, 2, 2 };
    Test("Test4", numbers, sizeof(numbers) / sizeof(int), 2, false);
}

// 输入空指针
void Test5() {
    int numbers[] = { 1 };
    Test("Test5", numbers, 1, 1, false);
}

// 输入空指针
void Test6() {
    Test("Test6", NULL, 0, 0, true);
}

int main(int argc, char** argv) {
    Test1();
    Test2();
    Test3();
    Test4();
    Test5();
    Test6();

    return 0;
}

关于Partition方法：

// 《剑指Offer——名企面试官精讲典型编程题》代码
// 著作权所有者：何海涛

#include <stdlib.h>
#include <stdio.h>
#include "Array.h"
#include <exception>

// Random Partition
int RandomInRange(int min, int max) {
    int random = rand() % (max - min + 1) + min;
    return random;
}

void Swap(int* num1, int* num2) {
    int temp = *num1;
    *num1 = *num2;
    *num2 = temp;
}

int Partition(int data[], int length, int start, int end) {
    if (data == NULL || length <= 0 || start < 0 || end >= length) {
        printf("Invalid Parameters");
        throw new std::exception();//这里括号里为什么不能加msg？？？！！！
    }
    int index = RandomInRange(start, end);
    Swap(&data[index], &data[end]);

    int small = start - 1;
    for (index = start; index < end; ++index) {
        if (data[index] < data[end]) {
            ++small;
            if (small != index)
                Swap(&data[index], &data[small]);
        }
    }

    ++small;
    Swap(&data[small], &data[end]);

    return small;
}