Sync LeetCode submission Runtime - 101 ms (49.50%), Memory - 83.4 MB (40.13%)

Author: koralkulacoglu

LeetCode/1447-jump-game-iv/README.md

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+<p>Given an array of&nbsp;integers <code>arr</code>, you are initially positioned at the first index of the array.</p>
+
+<p>In one step you can jump from index <code>i</code> to index:</p>
+
+<ul>
+	<li><code>i + 1</code> where:&nbsp;<code>i + 1 &lt; arr.length</code>.</li>
+	<li><code>i - 1</code> where:&nbsp;<code>i - 1 &gt;= 0</code>.</li>
+	<li><code>j</code> where: <code>arr[i] == arr[j]</code> and <code>i != j</code>.</li>
+</ul>
+
+<p>Return <em>the minimum number of steps</em> to reach the <strong>last index</strong> of the array.</p>
+
+<p>Notice that you can not jump outside of the array at any time.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> arr = [100,-23,-23,404,100,23,23,23,3,404]
+<strong>Output:</strong> 3
+<strong>Explanation:</strong> You need three jumps from index 0 --&gt; 4 --&gt; 3 --&gt; 9. Note that index 9 is the last index of the array.
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> arr = [7]
+<strong>Output:</strong> 0
+<strong>Explanation:</strong> Start index is the last index. You do not need to jump.
+</pre>
+
+<p><strong class="example">Example 3:</strong></p>
+
+<pre>
+<strong>Input:</strong> arr = [7,6,9,6,9,6,9,7]
+<strong>Output:</strong> 1
+<strong>Explanation:</strong> You can jump directly from index 0 to index 7 which is last index of the array.
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= arr.length &lt;= 5 * 10<sup>4</sup></code></li>
+	<li><code>-10<sup>8</sup> &lt;= arr[i] &lt;= 10<sup>8</sup></code></li>
+</ul>

LeetCode/1447-jump-game-iv/solution.cpp

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+class Solution {
+public:
+    int minJumps(vector<int>& arr) {
+        int n = arr.size();
+        if (n == 0) return 0;
+        unordered_map<int, vector<int>> nums;
+        unordered_map<int, bool> numsVis;
+        for (int i=0; i<n; i++) nums[arr[i]].push_back(i);
+        vector<int> dist(n, 1e9);
+        dist[0] = 0;
+        queue<int> q;
+        q.push(0);
+        while (!q.empty()) {
+            int node = q.front();
+            q.pop();
+            if (node < n-1 && dist[node+1] == 1e9) {
+                dist[node+1] = dist[node] + 1;
+                q.push(node+1);
+            }
+            if (node > 0 && dist[node-1] == 1e9) {
+                dist[node-1] = dist[node] + 1;
+                q.push(node-1);
+            }
+            if (numsVis[arr[node]]) continue;
+            for (int neigh : nums[arr[node]]) {
+                if (dist[neigh] == 1e9) {
+                    dist[neigh] = dist[node] + 1;
+                    q.push(neigh);
+                }
+            }
+            numsVis[arr[node]] = true;
+        }
+        return dist[n-1];
+    }
+};