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CyC2018 2020-02-24 00:37:17 +08:00
parent a5697cd803
commit e3793d43ea
2 changed files with 56 additions and 44 deletions

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@ -34,7 +34,7 @@
<div align="center"> <img src="https://cs-notes-1256109796.cos.ap-guangzhou.myqcloud.com/95903878-725b-4ed9-bded-bc4aae0792a9.jpg"/> </div><br>
广度优先搜索一层一层地进行遍历每层遍历都以上一层遍历的结果作为起点遍历一个距离能访问到的所有节点需要注意的是遍历过的节点不能再次被遍历
广度优先搜索一层一层地进行遍历每层遍历都以上一层遍历的结果作为起点遍历一个距离能访问到的所有节点需要注意的是遍历过的节点不能再次被遍历
第一层
@ -75,33 +75,39 @@
题目描述0 表示可以经过某个位置求解从左上角到右下角的最短路径长度
```java
public int shortestPathBinaryMatrix(int[][] grids) {
int[][] direction = {{1, -1}, {1, 0}, {1, 1}, {0, -1}, {0, 1}, {-1, -1}, {-1, 0}, {-1, 1}};
int m = grids.length, n = grids[0].length;
Queue<Pair<Integer, Integer>> queue = new LinkedList<>();
queue.add(new Pair<>(0, 0));
int pathLength = 0;
while (!queue.isEmpty()) {
int size = queue.size();
pathLength++;
while (size-- > 0) {
Pair<Integer, Integer> cur = queue.poll();
int cr = cur.getKey(), cc = cur.getValue();
grids[cr][cc] = 1; // 标记
for (int[] d : direction) {
int nr = cr + d[0], nc = cc + d[1];
if (nr < 0 || nr >= m || nc < 0 || nc >= n || grids[nr][nc] == 1) {
public int shortestPathBinaryMatrix(int[][] grids) {
if (grids == null || grids.length == 0 || grids[0].length == 0) {
return -1;
}
int[][] direction = {{1, -1}, {1, 0}, {1, 1}, {0, -1}, {0, 1}, {-1, -1}, {-1, 0}, {-1, 1}};
int m = grids.length, n = grids[0].length;
Queue<Pair<Integer, Integer>> queue = new LinkedList<>();
queue.add(new Pair<>(0, 0));
int pathLength = 0;
while (!queue.isEmpty()) {
int size = queue.size();
pathLength++;
while (size-- > 0) {
Pair<Integer, Integer> cur = queue.poll();
int cr = cur.getKey(), cc = cur.getValue();
if (grids[cr][cc] == 1) {
continue;
}
if (nr == m - 1 && nc == n - 1) {
return pathLength + 1;
if (cr == m - 1 && cc == n - 1) {
return pathLength;
}
grids[cr][cc] = 1; // 标记
for (int[] d : direction) {
int nr = cr + d[0], nc = cc + d[1];
if (nr < 0 || nr >= m || nc < 0 || nc >= n) {
continue;
}
queue.add(new Pair<>(nr, nc));
}
queue.add(new Pair<>(nr, nc));
}
}
return -1;
}
return -1;
}
```
## 2. 组成整数的最小平方数数量

View File

@ -34,7 +34,7 @@
<div align="center"> <img src="https://cs-notes-1256109796.cos.ap-guangzhou.myqcloud.com/95903878-725b-4ed9-bded-bc4aae0792a9.jpg"/> </div><br>
广度优先搜索一层一层地进行遍历每层遍历都以上一层遍历的结果作为起点遍历一个距离能访问到的所有节点需要注意的是遍历过的节点不能再次被遍历
广度优先搜索一层一层地进行遍历每层遍历都以上一层遍历的结果作为起点遍历一个距离能访问到的所有节点需要注意的是遍历过的节点不能再次被遍历
第一层
@ -75,33 +75,39 @@
题目描述0 表示可以经过某个位置求解从左上角到右下角的最短路径长度
```java
public int shortestPathBinaryMatrix(int[][] grids) {
int[][] direction = {{1, -1}, {1, 0}, {1, 1}, {0, -1}, {0, 1}, {-1, -1}, {-1, 0}, {-1, 1}};
int m = grids.length, n = grids[0].length;
Queue<Pair<Integer, Integer>> queue = new LinkedList<>();
queue.add(new Pair<>(0, 0));
int pathLength = 0;
while (!queue.isEmpty()) {
int size = queue.size();
pathLength++;
while (size-- > 0) {
Pair<Integer, Integer> cur = queue.poll();
int cr = cur.getKey(), cc = cur.getValue();
grids[cr][cc] = 1; // 标记
for (int[] d : direction) {
int nr = cr + d[0], nc = cc + d[1];
if (nr < 0 || nr >= m || nc < 0 || nc >= n || grids[nr][nc] == 1) {
public int shortestPathBinaryMatrix(int[][] grids) {
if (grids == null || grids.length == 0 || grids[0].length == 0) {
return -1;
}
int[][] direction = {{1, -1}, {1, 0}, {1, 1}, {0, -1}, {0, 1}, {-1, -1}, {-1, 0}, {-1, 1}};
int m = grids.length, n = grids[0].length;
Queue<Pair<Integer, Integer>> queue = new LinkedList<>();
queue.add(new Pair<>(0, 0));
int pathLength = 0;
while (!queue.isEmpty()) {
int size = queue.size();
pathLength++;
while (size-- > 0) {
Pair<Integer, Integer> cur = queue.poll();
int cr = cur.getKey(), cc = cur.getValue();
if (grids[cr][cc] == 1) {
continue;
}
if (nr == m - 1 && nc == n - 1) {
return pathLength + 1;
if (cr == m - 1 && cc == n - 1) {
return pathLength;
}
grids[cr][cc] = 1; // 标记
for (int[] d : direction) {
int nr = cr + d[0], nc = cc + d[1];
if (nr < 0 || nr >= m || nc < 0 || nc >= n) {
continue;
}
queue.add(new Pair<>(nr, nc));
}
queue.add(new Pair<>(nr, nc));
}
}
return -1;
}
return -1;
}
```
## 2. 组成整数的最小平方数数量