【JS】欧拉路径实现(回溯实现、栈实现)
来源:10-7 欧拉路径和本章小结
Potter520
2023-05-12
方式1:回溯实现
function findEulerPath(graph) {
let cc = new CC(graph);
if (cc.cccount() != 1) {
return [];
}
let startv = 0;
let cnt = 2;
for (let i = 0; i < graph.V(); i++) {
if (graph.degree(i) % 2 != 0) {
cnt--;
startv = i;
}
}
//! 说明:如果存在2个以上度<2的顶点,就不存在欧拉路径,直接返回
if (cnt < 0) {
return [];
}
let E = graph.E();
let res = [];
let count = 0;
function print(...args) {
// console.log("-".repeat(count), ...args);
}
function dfs(v, path) {
count++;
path.push(v);
//! 说明:当前的边数全部遍历完,说明找到解
if (graph.E() == 0) {
res = path.slice(0);
print("find solution: ", res);
return true;
}
//! 说明:需要把当前顶点的相邻顶点copy出来,如果不copy出来就会导致for循环的是循环。for里面不能边删除又添加
let edges = [...graph.adj(v).values()];
for (const w of edges) {
//! 遍历操作
graph.deleteEdge(v, w);
print("push:", path);
if (dfs(w, path)) {
return true;
}
//! 回溯操作
graph.addEdge(v, w);
path.pop();
print("pop:", path);
}
count--;
return false;
}
for (let i = 0; i < graph.V(); i++) {
if (i != startv) {
continue;
}
let isFindPath = dfs(i, []);
if (isFindPath) {
return res;
}
}
return [];
}
let res = findEulerPath(new Graph(path.resolve(__dirname, "./assets/g0.txt")));
console.log(res.join("->"));
res = findEulerPath(new Graph(path.resolve(__dirname, "./assets/g.txt")));
console.log(res.join("->"));
方式2:利用栈实现
function findEulerPath(graph) {
let cc = new CC(graph);
if (cc.cccount() != 1) {
return [];
}
let startv = 0;
let cnt = 2;
for (let i = 0; i < graph.V(); i++) {
if (graph.degree(i) % 2 != 0) {
cnt--;
startv = i;
}
}
//! 说明:如果存在2个以上度<2的顶点,就不存在欧拉路径,直接返回
if (cnt < 0) {
return [];
}
let g = graph.clone();
let res = [];
let stack = [];
let curv = startv;
stack.push(curv);
while (stack.length != 0) {
if (g.degree(curv) != 0) {
let w = g.adj(curv).values().next().value;
stack.push(curv);
g.deleteEdge(curv, w);
curv = w;
} else {
res.push(curv);
curv = stack.pop();
}
}
return res;
}
let res = findEulerPath(new Graph(path.resolve(__dirname, "./assets/g0.txt")));
console.log(res.join("->"));
res = findEulerPath(new Graph(path.resolve(__dirname, "./assets/g.txt")));
console.log(res.join("->"));
测试数据
- g0.txt
5 5
0 1
1 2
1 3
1 4
3 4
测试结果:
-------------------------------------1.回溯法-----------------------------
2->1->3->4->1->0
-------------------------------------2.Hierholzer - 栈实现-----------------------------
0->1->4->3->1->2
- g.txt
5 6
0 1
0 2
1 2
1 3
1 4
3 4
-------------------------------------1.回溯法-----------------------------
0->1->3->4->1->2->0
-------------------------------------2.Hierholzer - 栈实现-----------------------------
0->2->1->4->3->1->0
栈的实现,求欧拉路径和欧拉回路,仅仅只是加了一段边的合法校验+startv遍历起始点,其他代码就是欧拉回路栈实现代码,请问老师我的实现有问题吗?
写回答
1回答
-
我没有看出问题,以后遇到和欧拉回路相关的问题(通常在面试问题中其实很少见),可以使用自己的代码再测试一遍:)
感谢分享!继续加油!:)
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