基础算法——数组

/*************************************************************************
    > File Name: array.cpp
    > Author: xinyang
    > Mail: xuechen.xy@gmail.com 
    > Created Time: Tue 06 Oct 2015 03:14:34 PM CST
 ************************************************************************/

#include <iostream>
#include <algorithm>
#include <cstring>
#include <cstdio>
using namespace std;

/*
 * 斐波那契数列
 */
int fibonacci(int n) {
    if (n == 0 || n == 1) {
        return n;
    }

    int a = 0, b = 1;
    for (int i = 2; i <= n; ++i) {
        int tmp = a + b;
        a = b;
        b = tmp;
    }
    return b;
}

/*
 * 调整数组，将奇数放在所有偶数的前面
 */
void reorder_odd_even(int A[], int n) {
    if (A == NULL || n <= 0) {
        return;
    }

    int low = 0, high = n - 1;
    while (low < high) {
        while (low < high && (A[low] & 0x1) == 1) {
            ++low;
        }
        while (low < high && (A[high] & 0x1) == 0) {
            --high;
        }
        if (low < high) {
            int tmp = A[low];
            A[low] = A[high];
            A[high] = tmp;
        }
    }
}

/*
 * 顺时针打印矩阵
 */
void print_matrix_in_circle(int A[][4], int columns, int rows, int start) {
    int endX = columns - 1 - start;
    int endY = rows - 1 - start;

    for (int i = start; i <= endX; ++i) {
        cout << A[start][i] << ' ';
    }

    if (start < endY) {
        for (int i = start + 1; i <= endY; ++i) {
            cout << A[i][endX] << ' ';
        }
    }

    if (start < endX && start < endY) {
        for (int i = endX - 1; i >= start; --i) {
            cout << A[endY][i] << ' ';
        }
    }

    if (start <= endX && start < endY - 1) {
        for (int i = endY - 1; i >= start + 1; --i) {
            cout << A[i][start] << ' ';
        }
    }
}

void print_matrix_clock_wisely(int A[][4], int columns, int rows) {
    if (A == NULL || columns <= 0 || rows <= 0) {
        return;
    }
    int start = 0;
    while (columns > start * 2 && rows > start * 2) {
        print_matrix_in_circle(A, columns, rows, start);
        ++start;
    }
}

/*
 * 数组中超过一半的数字
 */
int partition(int A[], int low, int high) {
    int pivot = A[low];
    while (low < high) {
        while (low < high && A[high] >= pivot) {
            --high;
        }
        A[low] = A[high];
        while (low < high && A[low] <= pivot) {
            ++low;
        }
        A[high] = A[low];
    }
    A[low] = pivot;
    return low;
}

bool check_more_than_half(int A[], int n, int result) {
    int time = 0, half = n / 2;
    for (int i = 0; i < n; ++i) {
        if (A[i] == result) {
            ++ time;
            if (time > half) {
                return true;
            }
        }
    }
    return false;
}

int more_than_half_num1(int A[], int n) {
    if (A == NULL || n <= 0) {
        return -1;
    }

    int low = 0, high = n - 1, mid = (low + high) / 2;
    int pivotpos = partition(A, low, high);
    while (pivotpos != mid) {
        if (pivotpos > mid) {
            high = pivotpos - 1;
            pivotpos = partition(A, low, high);
        } else {
            low = pivotpos + 1;
            pivotpos = partition(A, low, high);
        }
    }

    int result = A[mid];
    if (!check_more_than_half(A, n, result)) {
        result = -1;
    }
    return result;
}

int more_than_half_num2(int A[], int n) {
    if (A == NULL || n <= 0) {
        return 0;
    }
    
    int result = A[0];
    int time = 1;
    for (int i = 1; i < n; ++i) {
        if (time == 0) {
            result = A[i];
            time = 1;
        } else if (A[i] == result) {
            ++time;
        } else {
            --time;
        }
    }
    if (!check_more_than_half(A, n, result)) {
        result = -1;
    }
    return result;
}

/*
 * 最小的k个数
 */
void get_least_k_num(int A[], int n, int output[], int k) {
    if (A == NULL || k <= 0
            || output == NULL || k <= 0 || k > n) {
        return;
    }

    int low = 0, high = n - 1;
    int pivotpos = partition(A, low, high);
    while (pivotpos != k - 1) {
        if (pivotpos > k - 1) {
            high = pivotpos - 1;
            pivotpos = partition(A, low, high);
        } else {
            low = pivotpos + 1;
            pivotpos = partition(A, low, high);
        }
    }

    for (int i = 0; i < k; ++i) {
        output[i] = A[i];
    }
}

/*
 * 连续字数组的最大和
 */
int get_greatest_continous_num(int A[], int n) {
    if (A == NULL || n <= 0) {
        return -1;
    }

    int cur_sum = 0;
    int ret = 0x80000000;
    for (int i = 0; i < n; ++i) {
        if (cur_sum <= 0) {
            cur_sum = A[i];
        } else {
            cur_sum += A[i];
        }
        if(cur_sum > ret) {
            ret = cur_sum;
        }
    }
    return ret;
}

/*
 * 把数组排成最小的数
 */
char *combine_str1 = new char[100];
char *combine_str2 = new char[100];
int cmp(char *str1, char *str2) {
    strcpy(combine_str1, str1);
    strcat(combine_str1, str2);

    strcpy(combine_str2, str2);
    strcat(combine_str2, str1);

    return strcmp(combine_str1, combine_str2);
}

void print_min_number(int A[], int n) {
    if (A == NULL || n <= 0) {
        return;
    }

    char **str_nums = (char **)(new int[n]);
    for (int i = 0; i < n; ++i) {
        str_nums[i] = new char[100];
        sprintf(str_nums[i], "%d", A[i]);
    }

    sort(str_nums, str_nums + n, cmp);
    for (int i = 0; i < n; ++i) {
        cout << str_nums[i];
    }
    for (int i = 0; i < n; ++i) {
        delete[] str_nums[i];
    }
    delete[] str_nums;
}

/*
 * 获取排序数组中指定数字的个数
 */
int get_first_k(int A[], int n, int k, int low, int high) {
    if (low > high) {
        return -1;
    }

    int mid = (low + high) / 2;
    int val_mid = A[mid];
    if (val_mid == k) {
        if ((mid > 0 && A[mid - 1] != k)
                || mid == 0) {
            return mid;
        } else {
            high = mid - 1;
        }
    } else if (val_mid > k) {
        high = mid - 1;
    } else {
        low = mid + 1;
    }

    return get_first_k(A, n, k, low, high);
}

int get_last_k(int A[], int n, int k, int low, int high) {
    if (low > high) {
        return -1;
    }

    int mid = (low + high) / 2;
    int val_mid = A[mid];
    if (val_mid == k) {
        if ((mid < n - 1 && A[mid + 1] != k)
                || mid == n - 1) {
            return mid;
        } else {
            low = mid + 1;
        }
    } else if (val_mid > k) {
        high = mid - 1;
    } else {
        low = mid + 1;
    }

    return get_last_k(A, n, k, low, high);
}

int get_num_of_k(int A[], int n, int k) {
    int num = 0;
    if (A == NULL || n <= 0) {
        return num;
    }

    int first = get_first_k(A, n, k, 0, n - 1);
    int last = get_last_k(A, n, k, 0, n - 1);
    if (first > -1 && last > -1) {
        num = last - first + 1;
    }
    return num;
}

/*
 * 和为s的两个数
 */
bool find_nums_with_sum(int A[], int n, int sum, int &num1, int &num2) {
    if (A == NULL || n <= 0) {
        return false;
    }

    int low = 0, high = n - 1;
    while (low < high) {
        long long cur_sum = A[low] + A[high];
        if (cur_sum == sum) {
            num1 = A[low];
            num2 = A[high];
            return true;
        } else if (cur_sum > sum) {
            --high;
        } else {
            ++low;
        }
    }
    return false;
}

/*
 * 和为s的连续正数序列
 */
void print_sequence(int small, int big) {
    for (int i = small; i <= big; ++i) {
        cout << i << ' ';
    }
}

void find_continuos_sequence(int sum) {
    if (sum < 3) {
        return;
    }

    int small = 1, big = 2;
    int mid = (1 + sum) / 2;
    int cur_sum = small + big;
    while (small < mid) {
        if (cur_sum == sum) {
            print_sequence(small, big);
        }
        while (cur_sum > sum && small < mid) {
            cur_sum -= small;
            ++small;
            if (cur_sum == sum) {
                print_sequence(small, big);
            }
        }
        ++big;
        cur_sum += big;
    }
}

/*
 * 扑克牌顺子（癞子斗地主）
 */
bool is_continuos(int A[], int n) {
    bool ret = false;
    if (A == NULL || n <= 0) {
        return ret;
    }

    sort(A, A + n);
    int zero = 0, gap = 0;
    for (int i = 0; i < n && A[i] == 0;
            ++i) {
        ++zero;
    }

    int small = zero, big = small + 1;
    while (big < n) {
        if (A[small] == A[big]) {
            return ret;
        }
        gap += (A[big] - A[small] - 1);
        small = big;
        ++big;
    }

    if (gap <= zero) {
        ret = true;
    }
    return ret;
}

int main() {
    cout << "fibonacci" << endl;
    cout << fibonacci(5) << endl << endl;

    cout << "reorder odd and even" << endl;
    int A[] = {3, 8, 7, 1, 2, 5, 4, 6, 9};
    reorder_odd_even(A, 9);
    for (int i = 0; i < 9; ++i) {
        cout << A[i] << ' ';
    }
    cout << endl << endl;

    cout << "print a matrix clockwisely" << endl;
    int B[][4] = {
        1, 2, 8, 9,
        2, 4, 9, 12,
        4, 7, 10, 13,
        6, 8, 11, 15};
    print_matrix_clock_wisely(B, 4, 4);
    cout << endl << endl;

    cout << "more than half" << endl;
    int C[] = {1, 2, 3, 1, 1};
    // cout << more_than_half_num1(C, 5) << endl << endl;
    cout << more_than_half_num2(C, 5) << endl << endl;

    cout << "get least k numbers" << endl;
    int output[5];
    get_least_k_num(A, 9, output, 5);
    for (int i = 0; i < 5; ++i) {
        cout << output[i] << ' ';
    }
    cout << endl << endl;

    cout << "get greatest continuos numbers" << endl;
    cout << get_greatest_continous_num(A, 9) << endl << endl;

    cout << "print minimum number" << endl;
    int D[] = {3, 32, 321};
    print_min_number(D, 3);
    cout << endl <<endl;

    cout << "get number of k" << endl;
    int E[] = {1, 2, 3, 3, 3, 4, 5};
    cout << get_num_of_k(E, 7, 3) << endl <<endl;;

    cout << "find two numbers with their sum" << endl;
    int num1, num2;
    find_nums_with_sum(E, 7, 5, num1, num2);
    cout << "number1: " << num1 << " number2: " << num2 << endl << endl;

    cout << "find continuos sequence" << endl;
    find_continuos_sequence(45);
    cout << endl << endl;

    int F[]= {0, 0, 1, 3, 4};
    if (true == is_continuos(F, 5)) {
        cout << "is continuos" << endl << endl;
    } else {
        cout << "is not continuos" << endl << endl;
    }

    return 0;
}