|
|
package class_2022_01_1_week;
|
|
|
|
|
|
import java.util.PriorityQueue;
|
|
|
|
|
|
// 来自学员问题
|
|
|
// 给定一个二维数组，其中全是非负数
|
|
|
// 每一步都可以往上、下、左、右四个方向运动
|
|
|
// 走过的路径，会沿途累加数字
|
|
|
// 返回从左下角走到右下角的累加和最小的多少
|
|
|
public class Code04_MinDistanceFromLeftUpToRightDownWalk4Directions {
|
|
|
|
|
|
public static int bestWalk1(int[][] map) {
|
|
|
int n = map.length;
|
|
|
int m = map[0].length;
|
|
|
int step = n * m - 1;
|
|
|
return process(map, n, m, step, 0, 0, 0, 0);
|
|
|
}
|
|
|
|
|
|
public static int process(int[][] map, int n, int m, int limit, int step, int row, int col, int cost) {
|
|
|
if (row < 0 || row == n || col < 0 || col == m || step > limit) {
|
|
|
return Integer.MAX_VALUE;
|
|
|
}
|
|
|
if (row == n - 1 && col == m - 1) {
|
|
|
return cost + map[row][col];
|
|
|
}
|
|
|
cost += map[row][col];
|
|
|
int p1 = process(map, n, m, limit, step + 1, row - 1, col, cost);
|
|
|
int p2 = process(map, n, m, limit, step + 1, row + 1, col, cost);
|
|
|
int p3 = process(map, n, m, limit, step + 1, row, col - 1, cost);
|
|
|
int p4 = process(map, n, m, limit, step + 1, row, col + 1, cost);
|
|
|
return Math.min(Math.min(p1, p2), Math.min(p3, p4));
|
|
|
}
|
|
|
|
|
|
public static int bestWalk2(int[][] map) {
|
|
|
|
|
|
int n = map.length;
|
|
|
int m = map[0].length;
|
|
|
// 堆
|
|
|
// 每一个对象，都是一个小数组
|
|
|
// {dis, row, col}
|
|
|
// 0 1 2
|
|
|
PriorityQueue<int[]> heap = new PriorityQueue<>((a, b) -> a[0] - b[0]);
|
|
|
// X,0,1 已经弹出了！ 以后在遇到(0,1)的事情，不管！
|
|
|
// poped记录哪些位置弹出，哪些没有！
|
|
|
boolean[][] poped = new boolean[n][m];
|
|
|
heap.add(new int[] { map[0][0], 0, 0 });
|
|
|
int ans = 0;
|
|
|
while (!heap.isEmpty()) {
|
|
|
int[] cur = heap.poll();
|
|
|
int dis = cur[0];
|
|
|
int row = cur[1];
|
|
|
int col = cur[2];
|
|
|
if (poped[row][col]) {
|
|
|
continue;
|
|
|
}
|
|
|
// 接下来就是要处理这个位置了！
|
|
|
poped[row][col] = true;
|
|
|
if (row == n - 1 && col == m - 1) {
|
|
|
ans = dis;
|
|
|
break;
|
|
|
}
|
|
|
add(dis, row - 1, col, n, m, map, poped, heap);
|
|
|
add(dis, row + 1, col, n, m, map, poped, heap);
|
|
|
add(dis, row, col - 1, n, m, map, poped, heap);
|
|
|
add(dis, row, col + 1, n, m, map, poped, heap);
|
|
|
}
|
|
|
return ans;
|
|
|
}
|
|
|
|
|
|
public static void add(int pre, int row, int col, int n, int m, int[][] map, boolean[][] used,
|
|
|
PriorityQueue<int[]> heap) {
|
|
|
if (row >= 0 && row < n && col >= 0 && col < m && !used[row][col]) {
|
|
|
heap.add(new int[] { pre + map[row][col], row, col });
|
|
|
}
|
|
|
}
|
|
|
|
|
|
// 为了测试
|
|
|
public static int[][] randomMatrix(int n, int m, int v) {
|
|
|
int[][] ans = new int[n][m];
|
|
|
for (int i = 0; i < n; i++) {
|
|
|
for (int j = 0; j < m; j++) {
|
|
|
ans[i][j] = (int) (Math.random() * v);
|
|
|
}
|
|
|
}
|
|
|
return ans;
|
|
|
}
|
|
|
|
|
|
// 为了测试
|
|
|
public static void main(String[] args) {
|
|
|
int n = 4;
|
|
|
int m = 4;
|
|
|
int v = 10;
|
|
|
int testTime = 10;
|
|
|
System.out.println("功能测试开始");
|
|
|
for (int i = 0; i < testTime; i++) {
|
|
|
int[][] map = randomMatrix(n, m, v);
|
|
|
int ans1 = bestWalk1(map);
|
|
|
int ans2 = bestWalk2(map);
|
|
|
if (ans1 != ans2) {
|
|
|
System.out.println("出错了!");
|
|
|
}
|
|
|
}
|
|
|
System.out.println("功能测试结束");
|
|
|
|
|
|
n = 1000;
|
|
|
m = 1000;
|
|
|
v = 100;
|
|
|
int[][] map = randomMatrix(n, m, v);
|
|
|
System.out.println("性能测试开始");
|
|
|
System.out.println("数据规模 : " + n + " * " + m);
|
|
|
System.out.println("值的范围 : 0 ~ " + v);
|
|
|
long start = System.currentTimeMillis();
|
|
|
bestWalk2(map);
|
|
|
long end = System.currentTimeMillis();
|
|
|
System.out.println("运行时间(毫秒) : " + (end - start));
|
|
|
System.out.println("性能测试结束");
|
|
|
}
|
|
|
|
|
|
}
|
