最长递增子序列

http://acm.tzc.edu.cn/acmhome/problemdetail.do;jsessionid=558B14243DB112F263306E7D3741A8A9?&method=showdetail&id=1052

在《编程之美》看过这题，中间利用二分查找可以把复杂度从O(N^2)降低到O(NlogN)

 

#include    <stdio.h>
#define        N        10001
 

int LIS(int * arr , int n)
{
    int        BIS[N+1] , nMaxLen;
    int        i , l , r , m , u;

    //Init
    BIS[1] = arr[0];    nMaxLen = 1;

    for(i = 1 ; i < n ; i++)
    {
        //BiSearch BIS[]
        l = 1;        r = nMaxLen;
        while(l + 1 < r)
        {
            m = (l + r) / 2;
            if(BIS[m] < arr[i])
                l = m;
            else
                r = m;
        }
        if(BIS[r] < arr[i])
            u = r;
        else if(BIS[l] < arr[i])
            u = l;
        else
            u = 0;

        //update BIS[]
        if(u == nMaxLen)
        {
            nMaxLen++;
            BIS[nMaxLen] = arr[i];
        }
        else
        {
            if(BIS[u+1] > arr[i])
                BIS[u+1] = arr[i];
        }
    }
    return    nMaxLen;
}

int main(void)
{
    int arr[N] , n ,i;

    while(scanf("%d", &n) != EOF )
    {
        for(i = 0 ;i < n ; i++)
            scanf("%d", arr + i);

        printf("%d\n",LIS(arr,n));
    }

    return    0;
}