Create Solution.js

solution/2000-2099/2097.Valid Arrangement of Pairs/Solution.js

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+/**
+ * @param {number[][]} pairs
+ * @return {number[][]}
+ */
+var validArrangement = function(pairs) {
+    const graph = new Map();
+    const indegree = new Map();
+    const outdegree = new Map();
+
+    for (const [start, end] of pairs) {
+        if (!graph.has(start)) graph.set(start, []);
+        graph.get(start).push(end);
+
+        outdegree.set(start, (outdegree.get(start) || 0) + 1);
+        indegree.set(end, (indegree.get(end) || 0) + 1);
+    }
+
+    let startNode = pairs[0][0];
+    for (const [node, out] of outdegree) {
+        const inCount = indegree.get(node) || 0;
+        if (out - inCount === 1) {
+            startNode = node;
+            break;
+        }
+    }
+
+    const result = [];
+    const stack = [startNode];
+
+    while (stack.length) {
+        const node = stack[stack.length - 1];
+        if (graph.has(node) && graph.get(node).length > 0) {
+            stack.push(graph.get(node).pop());
+        } else {
+            result.push(stack.pop());
+        }
+    }
+
+    result.reverse();
+
+    const output = [];
+    for (let i = 1; i < result.length; i++) {
+        output.push([result[i - 1], result[i]]);
+    }
+
+    return output;
+};