很显然,这道题目用二分搜索去解答,关键是怎么样去找这个上限点和下限点,方法很简单,每次去mid, 如果aa[mid] 比key要大的话,那么mid 是key的一个上限,但不一定是最小上限,同理。。。那么不断二分,不断逼近,最后即可求得解
void search_between(int arr[], int n_size, int *up, int *down,int key) { int left = 0; int right = n_size - 1; *up = INT_MAX; *down = INT_MIN; while(left <= right) { int mid = (left + right)>>1; if(arr[mid] < key) { *down = mid; left = mid + 1; } else { *up = mid; right = mid - 1; } } }