2分查找法

二分查找法

二分法的前提是：数据量就大，比如在一个很长的字符串中查某个字符；还有就是查找的数据必须是排好序的。

递归

int search(int data, int[] your_array, int low, int high){    int mid = (low+high)/2;    if (your_array[mid] > data)    { return search(data, your_array, mid+1, high); }    else if (your_array[mid] < data)    { return search(data, your_array, low, mid-1); }    else if (your_array[mid] == data)    { return your_array[mid];}    else return null;}

迭代int search(int data, int[] your_array){    int low = 0;    int high = your_array.Length;    int mid;    while(low != high)    {        mid = (low + high)/2;        if (your_array[mid] == data) return data;        else        {             if (your_array[mid] > data) { high = mid - 1;}            else if (your_array[mid] < data) { low = mid + 1;}        }        }    return null;}

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