算法面试笔记（二）数组

二分查找

static int binarySearch( int arr[], int target ) {

        int l = 0;
        int r = arr.length - 1; //查询[l,r]这个范围
        while( l <= r) {
            int mid = (r - l)/2 + l;
            if(arr[mid] == target) {
                return arr[mid];
            }else if(arr[mid] > target) {
                r = mid - 1;
            }else {
                l = mid + 1;
            }
        }
        return -1;
    }