UVA 714 Copying Books

Fucker — Tue, 19 Oct 2010 13:14:00 GMT

二分+贪心�Q�这�U�题目一直都是自��q��软肋�?/div>

此题��是一个最大值最��化的问题，诸如此类的什么最大最��，最��最大之�cȝ��首先惛_��的应该是二分�?/div>

二分��|��然后用贪心进行划分，在划分的时候需要注意分成k份，同时满��前面的尽可能的少。思�\��单，实现��h��有点�ȝ��?/div>

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <iostream>
using namespace std;

#define N 505

long long a[N];
int mk[N];

inline long long MAX(long long a, long long b)
{
    return a > b ? a : b;
}

long long Judge(long long mid, const int m, const int k)
{
    long long sum = 0, maxt = 0;
    for(int i = m - 1, j = 0; i >= 0; i--)
    {
        if(j < k - 1 && (i < k - j - 1 || sum + a[i] > mid))
        {
            maxt = MAX(sum, maxt);
            sum = a[i];
            mk[i] = 1;
            j++;
        }
        else sum += a[i];
    }
    return MAX(maxt, sum);
}

int main()
{
    int t, m, k;
    long long left, right, mid, ans;
    scanf("%d", &t);
    while(t--)
    {
        scanf("%d %d", &m, &k);
        left = right = 0;
        for(int i = 0; i < m; i++)
        {
            scanf("%lld", &a[i]);
            right += a[i];
        }
        while(left < right)
        {
            mid = (left + right) >> 1;
            ans = Judge(mid, m, k);
            if(ans > mid) left = mid + 1;
            else right = mid;
        }
        memset(mk, 0, sizeof(mk));
        Judge(left, m, k);
        printf("%lld", a[0]);
        if(mk[0]) printf(" /");
        for(int i = 1; i < m; i++)
        {
            printf(" %lld", a[i]);
            if(mk[i]) printf(" /");
        }
        printf("\n");
    }
    return 0;
}

Fucker 2010-10-19 21:14 发表评论

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UVA 714 Copying Books