find_mid

int find_mid( int *a, int *b, int length){    if (length == 1)//这里应该根据中位数的定义取大小        return a[0]<b[0]?a[0]:b[0];    int i = length/2;    if (a[i] == b[i])        return a[i];    else if (a[i]<b[i])        return find_mid( a+i, b, length-i );    else        return find_mid( a, b+i, length-i );}