A* 寻路算法学习

#include <iostream>
#include <list>

struct POINT {
int X;
int Y;
};

// G: 起点到当前点的成本
// H: 当前点到终点的估算成本
// F: G,H之和
struct MapNode {
int G;
int H;
int F;
bool can_pass;
POINT pt;
MapNode* pParent;

MapNode() : G(0), H(0), F(0), can_pass(false), pParent(NULL) {}

bool operator==(const MapNode& other) {
return (other.pt.X == pt.X && other.pt.Y == pt.Y);
}

bool operator!=(const MapNode& other) {
return !(*this == other);
}
};

bool nodeCompare(MapNode* p1, MapNode* p2) {
return (p1->F <  p2->F);
}

int maps[20][30] = {
1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
1,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,
1,0,1,0,0,0,1,1,1,1,1,1,1,1,1,1,1,1,0,1,1,1,1,1,1,1,1,1,0,1,
1,0,1,1,1,0,1,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,1,0,1,
1,0,0,0,1,0,1,0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,1,0,1,
1,0,1,1,1,0,1,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,1,0,1,
1,0,1,0,1,0,1,0,0,0,0,0,0,0,0,0,0,1,0,1,1,1,1,1,1,1,1,1,0,1,
1,0,1,0,1,0,1,1,1,1,1,1,1,1,1,1,0,1,0,0,0,0,0,0,0,0,0,1,0,1,
1,0,1,0,1,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,1,1,1,0,1,0,1,
1,0,1,0,1,1,1,1,1,1,1,1,1,1,1,1,0,1,0,0,0,0,0,0,0,0,0,1,0,1,
1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,1,1,1,1,1,1,1,1,1,0,1,
1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,1,0,0,0,0,0,0,0,0,0,1,0,1,
1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,1,1,1,0,1,0,1,
1,0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,1,0,0,0,0,0,0,0,0,0,1,0,1,
1,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,1,1,1,1,1,1,1,1,1,0,1,
1,0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,0,0,0,1,0,1,
1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,1,0,1,
1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,1,1,1,1,0,1,1,1,1,1,1,0,1,
1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,
1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1
};

MapNode* findNode(std::list<MapNode*>& nodes, const POINT& pt) {
for(std::list<MapNode*>::iterator it = nodes.begin();
it != nodes.end();
++it) {
if((*it)->pt.X == pt.X && (*it)->pt.Y == pt.Y) {
return *it;
}
}
return NULL;
}

void pathFinding() {
std::list<MapNode*> all;
std::list<MapNode*> open;
std::list<MapNode*> close;

for(int row=0; row<20; ++row) {
for(int col=0; col<30; ++col) {
MapNode* pNode = new MapNode;
pNode->pt.X = row;
pNode->pt.Y = col;
pNode->can_pass = (maps[row][col] == 0 ? true : false);
all.push_back(pNode);
}
}

POINT pt_start = {1, 1};
POINT pt_target = {10, 16};
MapNode* pStart = findNode(all, pt_start);
MapNode* pTarget = findNode(all, pt_target);

open.push_back(pStart);
while(!open.empty()) {
open.sort(nodeCompare);
MapNode *pNode = open.front();
if (*pNode == *pTarget) {
break;
}
open.pop_front();
close.push_back(pNode);
// 查找周围节点并将合适的加入open
int ptMask[8][3] = { // x坐标相对位置，y坐标相对位置，移动耗费
{-1, -1, 14}, // 左上
{0 , -1, 10}, // 正上
{1 , -1, 14}, // 右上
{-1, 0 , 10}, // 正左
{1 , 0 , 10}, // 正右
{-1, 1 , 14}, // 左下
{0 , 1 , 10}, // 正下
{1 , 1 , 14}  // 右下
};
for(int i=0; i<8; ++i) {
POINT pt;
pt.X = pNode->pt.X + ptMask[i][0];
pt.Y = pNode->pt.Y + ptMask[i][1];

if(pt.X > 0 && pt.X < 30 && pt.Y >0  && pt.Y < 20) {
MapNode* pChildNode = findNode(all, pt);
if(!pChildNode->can_pass || NULL != findNode(close, pt)) {
// 如果pNodeLT不可抵达的或者它在 close list 中，忽略它
} else {
if(NULL == findNode(open, pt)) {
// 如果pNodeLT不在 open list 中，把它加入 open list，
// 并且把当前方格设置为它的父亲，记录该方格的F,G和H值
pChildNode->pParent = pNode;
pChildNode->G = pChildNode->pParent->G + ptMask[i][2];
pChildNode->H = 10 * (abs(pTarget->pt.X - pt.X) + abs(pTarget->pt.Y - pt.Y));
pChildNode->F = pChildNode->G + pChildNode->H;
open.push_back(pChildNode);
} else {
// 如果pNodeLT已经在 open list 中，检查这条路径 ( 即经由
// 当前方格到达它那里 ) 是否更好，用 G 值作参考。更小的 G
// 值表示这是更好的路径
int tG = pNode->G + ptMask[i][2];
if(tG < pChildNode->G) {
pChildNode->pParent = pNode;
pChildNode->G = tG;
pChildNode->H = 10 * (abs(pTarget->pt.X - pt.X) + abs(pTarget->pt.Y - pt.Y));
pChildNode->F = pChildNode->G + pChildNode->H;
}
}
}
}
}
}
if(NULL != pTarget->pParent) {
MapNode* pNode = pTarget;
std::cout << "path is : " << std::endl;
do {
std::cout << "pt[" << pNode->pt.X << ", " << pNode->pt.Y << "] ->" << std::endl;
pNode = pNode->pParent;
} while(*pNode != *pStart);
std::cout << "pt[" << pNode->pt.X << ", " << pNode->pt.Y << "]" << std::endl;
}
}

int main() {

pathFinding();

system("pause");

return 0;
}