OJ3RD 1132 哈弗曼编码 - 贪心算法&哈夫曼树

链接：http://acm.buaa.edu.cn/problem/1132/

因为数据比较小就没怎么做优化 

顺便学习了一下哈夫曼编码...照着它说的把哈夫曼树立起来，然后报告文件大小就行了..

另外发现gcc有个怪脾气，struct内变量不能简单地像parent=-1这样初始赋值，而是要用如下代码中方法写一个构造函数

这和vs上有区别，vs  上前者是能通过的，但是gcc上会报compile  error

#include<iostream>
#include<cstdio>
using namespace std;
const int MAX = 0x3f3f3f3f;

struct huffmannode
{
int weight;
int parent, lchild, rchild;
huffmannode() :parent(-1), lchild(-1), rchild(-1) {}
};

huffmannode HF[1000];
int N;

void build_huffman_tree()
{
for (int i = 0; i < N - 1; i++)
{
int m1 = MAX, m2 = MAX;
int x1 = 0, x2 = 0;
for (int j = 0; j < i + N; j++)
{
if (HF[j].weight < m1&& HF[j].parent == -1)
{
m2 = m1;
x2 = x1;
m1 = HF[j].weight;
x1 = j;
}
else if (HF[j].weight < m2&& HF[j].parent == -1)
{
m2 = HF[j].weight;
x2 = j;
}
}
HF[x1].parent = N + i;
HF[x2].parent = N + i;
HF[N + i].weight = HF[x1].weight + HF[x2].weight;
HF[N + i].lchild = x1;
HF[N + i].rchild = x2;
}
}

int dist(int i)
{
if (HF[i].parent == -1) return 0;
else return dist(HF[i].parent) + 1;
}

int main()
{
while (~scanf("%d", &N))
{
for (int i = 0; i < 2 * N - 1; i++)
HF[i].lchild = HF[i].rchild = HF[i].parent = -1;
for (int i = 0; i < N; i++)
scanf("%d", &(HF[i].weight));
build_huffman_tree();
int ans = 0;
for (int i = 0; i < N; i++)
ans += HF[i].weight*dist(i);
printf("%d\n", ans);
}
return 0;
}