最佳答案
在C言語編程中，我們常常碰到各種複雜的算法成績。這些算法可能是排序、查抄、字符串處理等。而在這其中，「大年夜A」算法（平日指的是A*查抄算法）是一個非常有效的東西。本文將深刻剖析「大年夜A」算法的奧秘，並展示如何在一招中輕鬆控制它。
一、A*算法概述
A*算法是一種啟發式查抄算法，它結合了最佳優先查抄跟Dijkstra算法的長處。它的核心頭腦是評價每個節點的「總價值」，這個總價值由兩部分構成：現實本錢跟啟發式估計本錢。
- 現實本錢：從出發點到以後節點的現實間隔。
- 啟發式估計本錢：從以後節點到目標節點的估計間隔。
A*算法會優先抉擇總價值最小的節點停止擴大年夜，從而找到從出發點到目標的最短道路。
二、A*算法的C言語實現
下面是一個簡單的A*算法的C言語實現示例：
#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
#define MAX_NODES 1000
typedef struct {
int x, y;
} Point;
typedef struct {
Point point;
int g, h, f;
} Node;
Node openList[MAX_NODES];
Node closedList[MAX_NODES];
int openListSize = 0;
int closedListSize = 0;
int heuristic(Point a, Point b) {
return abs(a.x - b.x) + abs(a.y - b.y);
}
int findNode(Point p) {
for (int i = 0; i < openListSize; i++) {
if (openList[i].point.x == p.x && openList[i].point.y == p.y) {
return i;
}
}
return -1;
}
void addOpenList(Node node) {
openList[openListSize++] = node;
}
void addClosedList(Node node) {
closedList[closedListSize++] = node;
}
void removeOpenList(int index) {
for (int i = index; i < openListSize - 1; i++) {
openList[i] = openList[i + 1];
}
openListSize--;
}
int main() {
// 初始化出發點跟起點
Point start = {0, 0};
Point end = {5, 5};
// 增加出發點到開放列表
Node startNode = {start, 0, heuristic(start, end), 0};
addOpenList(startNode);
while (openListSize > 0) {
// 找到總價值最小的節點
int minIndex = 0;
for (int i = 1; i < openListSize; i++) {
if (openList[i].f < openList[minIndex].f) {
minIndex = i;
}
}
// 獲取以後節點
Node currentNode = openList[minIndex];
removeOpenList(minIndex);
addClosedList(currentNode);
// 假如達到起點，則結束
if (currentNode.point.x == end.x && currentNode.point.y == end.y) {
break;
}
// 擴小節點
Point neighbor;
neighbor.x = currentNode.point.x - 1;
neighbor.y = currentNode.point.y;
if (neighbor.x >= 0 && neighbor.y >= 0 && neighbor.x < 5 && neighbor.y < 5) {
int index = findNode(neighbor);
if (index == -1) {
Node neighborNode = {neighbor, currentNode.g + 1, heuristic(neighbor, end), currentNode.g + 1 + heuristic(neighbor, end)};
addOpenList(neighborNode);
} else {
if (currentNode.g + 1 < openList[index].g) {
openList[index].g = currentNode.g + 1;
openList[index].f = currentNode.g + 1 + heuristic(neighbor, end);
}
}
}
neighbor.x = currentNode.point.x + 1;
neighbor.y = currentNode.point.y;
if (neighbor.x >= 0 && neighbor.y >= 0 && neighbor.x < 5 && neighbor.y < 5) {
int index = findNode(neighbor);
if (index == -1) {
Node neighborNode = {neighbor, currentNode.g + 1, heuristic(neighbor, end), currentNode.g + 1 + heuristic(neighbor, end)};
addOpenList(neighborNode);
} else {
if (currentNode.g + 1 < openList[index].g) {
openList[index].g = currentNode.g + 1;
openList[index].f = currentNode.g + 1 + heuristic(neighbor, end);
}
}
}
neighbor.x = currentNode.point.x;
neighbor.y = currentNode.point.y - 1;
if (neighbor.x >= 0 && neighbor.y >= 0 && neighbor.x < 5 && neighbor.y < 5) {
int index = findNode(neighbor);
if (index == -1) {
Node neighborNode = {neighbor, currentNode.g + 1, heuristic(neighbor, end), currentNode.g + 1 + heuristic(neighbor, end)};
addOpenList(neighborNode);
} else {
if (currentNode.g + 1 < openList[index].g) {
openList[index].g = currentNode.g + 1;
openList[index].f = currentNode.g + 1 + heuristic(neighbor, end);
}
}
}
neighbor.x = currentNode.point.x;
neighbor.y = currentNode.point.y + 1;
if (neighbor.x >= 0 && neighbor.y >= 0 && neighbor.x < 5 && neighbor.y < 5) {
int index = findNode(neighbor);
if (index == -1) {
Node neighborNode = {neighbor, currentNode.g + 1, heuristic(neighbor, end), currentNode.g + 1 + heuristic(neighbor, end)};
addOpenList(neighborNode);
} else {
if (currentNode.g + 1 < openList[index].g) {
openList[index].g = currentNode.g + 1;
openList[index].f = currentNode.g + 1 + heuristic(neighbor, end);
}
}
}
}
return 0;
}
三、總結
經由過程本文的介紹，信賴你曾經對A*算法有了深刻的懂得。A*算法是一種非常實用的查抄算法，它可能利用於各種場景，如道路打算、迷宮求解等。控制A*算法，可能幫助你輕鬆處理很多複雜的編程成績。