title: 代码随想录 day53 第11章 图论part04
date: 2024-12-22 23:48:48
modificationDate: 2024 十二月 22日 星期日 23:48:48
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- carl
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**第十一章：图论part04**
经过上面的练习，大家可能会感觉 广搜不过如此，都刷出自信了，本题让大家初步感受一下，广搜难不在广搜本身，而是如何应用广搜。
https://www.programmercarl.com/kamacoder/0110.字符串接龙.html
```go
// ladderLength 实现 BFS 查找最短路径长度
func ladderLength(beginWord, endWord string, wordList \[\]string) int {
wordSet := make(mapstringstruct{})
for _, word := range wordList {
wordSetword = struct{}{}
}
if _, exists := wordSetendWord; !exists {
return 0
}
queue := \[\]string{beginWord}
visitMap := make(mapstringint)
visitMapbeginWord = 1
for len(queue) > 0 {
currentWord := queue0
queue = queue1:
path := visitMapcurrentWord
for i := 0; i < len(currentWord); i++ {
chars := \[\]rune(currentWord)
for ch := 'a'; ch <= 'z'; ch++ {
charsi = ch
newWord := string(chars)
if newWord == endWord {
return path + 1
}
if _, exists := wordSetnewWord; exists {
if _, visited := visitMapnewWord; !visited {
visitMapnewWord = path + 1
queue = append(queue, newWord)
}
}
}
}
}
return 0
}
```
深搜有细节，同样是深搜两种写法的区别，以及什么时候需要回溯操作呢？
https://www.programmercarl.com/kamacoder/0105.有向图的完全可达性.html
```python
import collections
path = set() # 纪录 BFS 所经过之节点
def bfs(root, graph):
global path
que = collections.deque(root)
while que:
cur = que.popleft()
path.add(cur)
for nei in graphcur:
que.append(nei)
graphcur = \[\]
return
def main():
N, K = map(int, input().strip().split())
graph = collections.defaultdict(list)
for _ in range(K):
src, dest = map(int, input().strip().split())
graphsrc.append(dest)
bfs(1, graph)
if path == {i for i in range(1, N + 1)}:
return 1
return -1
if name == "main":
print(main())
```
简单题，避免大家惯性思维，建议大家先独立做题。
https://www.programmercarl.com/kamacoder/0106.岛屿的周长.html
```python
def main():
import sys
input = sys.stdin.read
data = input().split()
读取 n 和 m
n = int(data0)
m = int(data1)
初始化 grid
grid = \[\]
index = 2
for i in range(n):
grid.append(int(data\[index + j) for j in range(m)])
index += m
sum_land = 0 # 陆地数量
cover = 0 # 相邻数量
for i in range(n):
for j in range(m):
if gridij == 1:
sum_land += 1
统计上边相邻陆地
if i - 1 >= 0 and gridi - 1j == 1:
cover += 1
统计左边相邻陆地
if j - 1 >= 0 and gridij - 1 == 1:
cover += 1
不统计下边和右边，避免重复计算
result = sum_land * 4 - cover * 2
print(result)
if name == "main":
main()
```