UVa 11292 Dragon of Loowater

　　很直接的一道题，排序比较就行了，不过还是超时了一次，因为一不小心写成死循环了。。。

　　代码如下:

#include <cstdio>
#include <algorithm>
using namespace std;

const int maxn = 20000+10;
int h[maxn], k[maxn];

int main()
{
#ifdef LOCAL
    freopen("in", "r", stdin);
#endif
    int n, m;
    while(scanf("%d%d", &n, &m) != EOF && n && m)
    {    
        for(int i = 0; i < n; i++)
            scanf("%d", &h[i]);
        for(int i = 0; i < m; i++)
            scanf("%d", &k[i]);
        sort(h, h+n);
        sort(k, k+m);
        int i, j = 0;
        int flag = 1;
        int sum = 0;
        for(i = 0; i < n; i++)
        {
            while(1)
            {
                if(j >= m)
                {
                    flag = 0;
                    break;
                }
                if(k[j] >= h[i])
                {
                    sum += k[j];
                    j++;
                    break;
                }
                j++;
            }
            if(!flag)   break;
        }
        if(!flag)   printf("Loowater is doomed!\n");
        else printf("%d\n", sum);
    }
    return 0;
}

　　这是开始写的代码，把头作外层循环，让每一个骑士去找头，不仅不合正常思维，而且代码长、难理解，后来看了下书，修改代码如下：

#include <cstdio>
#include <algorithm>
#define MAXN 20000+10
using namespace std;

int main()
{
#ifdef LOCAL
    freopen("in", "r", stdin);
#endif
    int h[MAXN], k[MAXN];    //h[] are dragon's heads and k[] are knights
    int n, m;    // n is the number of heads, m is the number of knights
    while (scanf("%d%d", &n, &m) != EOF)
    {
        if (n == 0 && m == 0) break;
        for (int i = 0; i < n; i++)   scanf("%d", &h[i]);
        for (int i = 0; i < m; i++)   scanf("%d", &k[i]);
        sort(h, h+n);
        sort(k, k+m);
        int cur = 0, cost = 0;
        for (int i = 0; i < m; i++)        // for each knight
            if (k[i] >= h[cur])
            {
                cost += k[i];
                if (++cur >= n)   break;
            }
        if (cur < n)   printf("Loowater is doomed!\n");
        else printf("%d\n", cost);
    }
    return 0;
}

　　这下感觉不错，自然，代码也短了。然后就像看看c能比c++快多少，就又改了一下，变成c版本：

#include <stdio.h>
#include <stdlib.h>
#define MAXN 20000+10

int cmp(const void *_a, const void *_b)
{
    int *a = (int*)_a;
    int *b = (int*)_b;
    return *a - *b;
}

int main()
{
#ifdef LOCAL
    freopen("in", "r", stdin);
#endif
    int h[MAXN], k[MAXN];    /* h[] are dragon's heads and k[] are knights */
    int n, m, i;    /* n is the number of heads, m is the number of knights */
    int cur, cost;
    while (scanf("%d%d", &n, &m) != EOF)
    {
        if (n == 0 && m == 0) break;
        for (i = 0; i < n; i++)   scanf("%d", &h[i]);
        for (i = 0; i < m; i++)   scanf("%d", &k[i]);
        qsort(h, n, sizeof(int), cmp);
        qsort(k, m, sizeof(int), cmp);
        cur = 0;
        cost = 0;
        for (i = 0; i < m; i++)        /* for each knight */
            if (k[i] >= h[cur])
            {
                cost += k[i];
                if (++cur >= n)   break;
            }
        if (cur < n)   printf("Loowater is doomed!\n");
        else printf("%d\n", cost);
    }
    return 0;
}

　　结果...c++的代码用了29ms，c的代码用了32ms，有点惊讶...不过还是喜欢c++的随处声明变量的方式，强大的STL函数库、还有习惯了的注释（//注释风格在gcc的ansi选项会出错），同时还不习惯c++式的输入输出，暂时还是用c的吧，等我发现c++输入输出的好处再改啦(*^__^*) 嘻嘻……