Complexity

⏰ Time complexity: O(n^2), where n is the size of the grid, since we process all rows and columns.
🧺 Space complexity: O(n^2), for storing serialized rows in the hash map.
Code

[{"language":"Java","code":"class Solution {\n    public int equalPairs(int[][] grid) {\n        int n = grid.length;\n        Map<String, Integer> rowCount = new HashMap<>();\n        for (int i = 0; i < n; i++) {\n            StringBuilder sb = new StringBuilder();\n            for (int j = 0; j < n; j++) {\n                sb.append(grid[i][j]).append(\",\");\n            }\n            String key = sb.toString();\n            rowCount.put(key, rowCount.getOrDefault(key, 0) + 1);\n        }\n        int ans = 0;\n        for (int j = 0; j < n; j++) {\n            StringBuilder sb = new StringBuilder();\n            for (int i = 0; i < n; i++) {\n                sb.append(grid[i][j]).append(\",\");\n            }\n            String key = sb.toString();\n            ans += rowCount.getOrDefault(key, 0);\n        }\n        return ans;\n    }\n}","lang":"java","html":"<pre class=\"shiki shiki-themes github-light github-dark\" style=\"background-color:#fff;--shiki-dark-bg:#24292e;color:#24292e;--shiki-dark:#e1e4e8\" tabindex=\"0\"><code><span class=\"line\"><span style=\"color:#D73A49;--shiki-dark:#F97583\">class</span><span style=\"color:#6F42C1;--shiki-dark:#B392F0\"> Solution</span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\"> {</span></span>\n<span class=\"line\"><span style=\"color:#D73A49;--shiki-dark:#F97583\">    public</span><span style=\"color:#D73A49;--shiki-dark:#F97583\"> int</span><span style=\"color:#6F42C1;--shiki-dark:#B392F0\"> equalPairs</span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\">(</span><span style=\"color:#D73A49;--shiki-dark:#F97583\">int</span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\">[][] </span><span style=\"color:#E36209;--shiki-dark:#FFAB70\">grid</span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\">) {</span></span>\n<span class=\"line\"><span style=\"color:#D73A49;--shiki-dark:#F97583\">        int</span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\"> n </span><span style=\"color:#D73A49;--shiki-dark:#F97583\">=</span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\"> grid.length;</span></span>\n<span class=\"line\"><span style=\"color:#24292E;--shiki-dark:#E1E4E8\">        Map&#x3C;</span><span style=\"color:#D73A49;--shiki-dark:#F97583\">String</span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\">, </span><span style=\"color:#D73A49;--shiki-dark:#F97583\">Integer</span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\">> rowCount </span><span style=\"color:#D73A49;--shiki-dark:#F97583\">=</span><span style=\"color:#D73A49;--shiki-dark:#F97583\"> new</span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\"> HashMap&#x3C;>();</span></span>\n<span class=\"line\"><span style=\"color:#D73A49;--shiki-d
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