[算法] 循环有序数组查找非递归实现

非递归实现

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

int isOrdered(int *array, int begin, int end) {
    return *(array+end) > *(array+begin) ? 1 : 0;
}

int contains(int *array, int begin, int end, int theNum) {
    return theNum >= *(array + begin) && theNum <= *(array + end) ? 1 : 0;
}

int CyclicOrderedBinarySearchNonRecursively(int *array, int begin, int end, int theNum) {

    while(end >= begin) {
        if(begin == end) {
            if(*(array + begin) == theNum) {
                return begin;
            } else {
                return -1;
            }
        }

        int mid = (begin + end) / 2;
        if(isOrdered(array, begin, mid)) {
            if(contains(array, begin, mid, theNum)) {
                end = mid;
            } else {
                begin = mid + 1;
            }

        } else {
            if(contains(array, mid + 1, end, theNum)) {
                begin = mid + 1;
            } else {
                end = mid;
            }
        }
    }
    return -1;
}

int search_nonrecursively(int *array, int n, int theNum) {
    return CyclicOrderedBinarySearchNonRecursively(array, 0, n - 1, theNum);
}

int main() {

    int *array = (int *)malloc(sizeof(int)*16);
    int i;
    for(i = 0; i < 16; i++) {
        *(array + i) = (i+5) % 16;
    }

    int ret = search_nonrecursively(array, 16, 10);
    printf("%d\n", ret);
    return 0;
}