POJ 1502 MPI Maelstrom

#include <iostream>
#include <cstring>
#define MAX_N 1000   //最大结点数
using namespace std;
//邻接表
struct head
{
int from, to, weight;
head * next;
head()
{
from = to = 0;
next = NULL;
}
}*heads[MAX_N + 1];
int dist[MAX_N + 1];             //记录最短路径
int n;
int heap[MAX_N + 1];           //邻接表
char temp[20];
bool inQueue[MAX_N + 1];   //标识当前节点是否在队列中
//插入边[from, to, weight]
void insert(int from, int to, int weight)
{
head *newNode = new head();
newNode->from = from;
newNode->to = to;
newNode->weight = weight;
newNode->next = heads[from];
heads[from] = newNode;
}
//结点p的左孩子
int left(int p)
{
return p * 2;
}
//结点p的右孩子
int right(int p)
{
return p * 2 + 1;
}
//结点p的父亲
int parent(int p)
{
return p / 2;
}
//取堆的大小
int heapSize()
{
return heap[0];
}
//增加堆的大小change
void changeHeapSize(int change)
{
heap[0] += change;
}
//比较两个堆元素对应结点的距离大小
int compare(int p1, int p2)
{
int dist1 = dist[heap[p1]];
int dist2 = dist[heap[p2]];
if(dist1 > dist2) return -1;
else if(dist1 == dist2) return 0;
else return 1;
}
//从结点n开始调整堆
void maxHeapify(int p)
{
int l = left(p), r = right(p), largest;
if(l <= heapSize() && compare(l, p) > 0)
largest = l;
else largest = p;
if(r <= heapSize() && compare(r, largest) > 0)
largest = r;
if(largest != p)
{
int temp = heap[p];
heap[p] = heap[largest];
heap[largest] = temp;
maxHeapify(largest);
}
}
//弹出堆中最大值
int popHeapMax()
{
if(heapSize() < 1) return -1;
int maxVal = heap[1];
inQueue[maxVal] = false;
heap[1] = heap[heapSize()];
changeHeapSize(-1);
maxHeapify(1);
return maxVal;
}
//得到val在堆中的下标
int getHeapPos(int val)
{
/*int curPos = 1;
while(heap[curPos] != 0 && heap[curPos] != val)
{
if(val < heap[curPos]) curPos = left(curPos);
else curPos = right(curPos);
}
return curPos;*/
for(int i = 1; i <= heapSize(); i++)
if(heap[i] == val)
return i;
return -1;
}
//更新堆，从pos往上更新
void updateHeapPos(int pos)
{
while(pos > 1 && compare(pos, parent(pos)) > 0)
{
int temp = heap[pos];
heap[pos] = heap[parent(pos)];
heap[parent(pos)] = temp;
pos = parent(pos);
}
}
插入堆元素
void heapInsert(int posVal)
{
changeHeapSize(1);
heap[heapSize()] = posVal;
updateHeapPos(heapSize());
}
void init()
{
heap[0] = 0;
//heap[1] = 1;
inQueue[0] = true;
for(int i = 1; i <= n; i++)
{
inQueue[i] = true;
heads[i] = NULL;
dist[i] = INT_MAX;
heapInsert(i);
}
dist[1] = 0;
}
void dijkstra()
{
while(heapSize() != 0)
{
int maxNode = popHeapMax();
int curDist = dist[maxNode];
head * curHead = heads[maxNode];
while(curHead != NULL)
{
int nextNode = curHead->to;
if(inQueue[nextNode])
{
if(curDist + curHead->weight < dist[nextNode])
{
dist[nextNode] = curDist + curHead->weight;
updateHeapPos(getHeapPos(nextNode));
}
}
curHead = curHead->next;
}
}
}
int getNum()
{
int i, len = strlen(temp), total = 0;
for(i = 0; i < len; i++)
total = total * 10 + int(temp[i] - '0');
return total;
}
int main()
{
int i, j;
scanf("%d", &n);
init();
for(i = 2; i <= n; i++)
{
for(j = 1; j < i; j++)
{
scanf("%s", temp);
if(temp[0] == 'x') continue;
int weight = getNum();
insert(i, j, weight);
insert(j, i, weight);
}
}
dijkstra();
int maxVal = -1;
for(i = 1; i <= n; i++)
if(dist[i] > maxVal)
maxVal = dist[i];
printf("%d/n", maxVal);
return 0;
}