面试常用查找算法

代码

方面适应所有算法，都使用有序数组

#include <stdio.h>
#include <stdlib.h>

// sequence search
int SequenceSearch(int* a, int value, int length) {
    int i;
    for (i = 0; i < length; i++) {
        if (*(a + i) == value) {
            return i;
        }
    }
    return -1;
}

// binary search        (sort)
int Binary_Search_rescur(int* a, int value, int low, int high) {
    int mid = (low + high) / 2;
    if (low < high && *(a + mid) == value) {
        return mid;
    } else if (low < high && *(a + mid) > value) {
        Binary_Search(a, value, low, mid - 1);
    } else if (low < high && *(a + mid) < value) {
        Binary_Search(a, value, mid + 1, high);
    } else {
        return -1;
    }
}
int Binary_Search(int* a, int value, int length) {
    int left = 0;
    int right = length;
    while (left <= right) {
        int mid = (left + right)/2;
        if (*(a + mid) == value) {
            return mid;
        } else if (*(a + mid) < value) {
            left = mid + 1;
        }
        else if (*(a + mid) > value) {
            right = mid - 1;
        }
    }
    return -1;
}

// insert search     (sort)
int Insert_Search(int* a, int value, int length) {
    int left = 0;
    int right = length;
    while (left <= right) {
        int mid = left + (value - *(a + left))/(*(a + right) - *(a + left)) * (right - left);
        if (*(a + mid) == value) {
            return mid;
        } else if (*(a + mid) < value) {
            left = mid + 1;
        } else if (*(a + mid) > value) {
            right = mid - 1;
        }
    }
    return -1;
}

// fibonacci search
void Make_Fib(int* fib, int size) {
    *fib = 1;
    *(fib + 1) = 1;
    int i;
    for (i = 2; i < size; i++) {
        *(fib + i) = *(fib + i - 1) + *(fib + i - 2);
    }
}
int Fibonacci_Search(int* a, int value, int length, int fib_size) {
    int left = 0;
    int right = length;
    int fib[fib_size];
    Make_Fib(fib, fib_size);
    int k = 0, i;
    while (right > *(fib + k)) {
        k++;
    }
    for (i = length + 1; i < *(fib + k); i++) {
        *(a + i) = *(a + length);
    }
    while (left <= right) {
        int mid = left + *(fib + k - 1) - 1;
        if (*(a + mid) == value) {
            if (mid <= length) {
                return mid;
            } else {
                return length;
            }
        } else if (*(a + mid) < value) {
            left = mid + 1;
            k -= 2;
        } else if (*(a + mid) > value) {
            right = mid - 1;
            k -= 1;
        }
    }
    return -1;
}

int main()
{
    int a[10] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
    int len = 10, num = 100, val, i;
    int fibn = 10;     // args for fibonacci array
    printf("a[10] = ");
    for (i = 0; i < 10; i++) {
        printf("%d ", *(a + i));
    }
    printf ("\nenter value : ");
    scanf("%d", &val);

    //num = SequenceSearch(a, val, len);
    //num = Binary_Search_rescur(a, val, 0, len - 1);
    //num = Binary_Search(a, val, len - 1);
    //num = Insert_Search(a, val, len - 1);
    num = Fibonacci_Search(a, val, len - 1, fibn);

    printf("value %d is num %d\n", val, num + 1);
    return 0;
}