{"id":63,"date":"2018-11-26T20:52:43","date_gmt":"2018-11-26T20:52:43","guid":{"rendered":"https:\/\/andybase.com\/?p=63"},"modified":"2019-05-03T18:04:50","modified_gmt":"2019-05-03T18:04:50","slug":"947-most-stones-removed-with-same-row-or-column","status":"publish","type":"post","link":"https:\/\/andybase.com\/?p=63","title":{"rendered":"947\t Most Stones Removed with Same Row or Column"},"content":{"rendered":"\n<p>Link:&nbsp;<a href=\"https:\/\/leetcode.com\/problems\/most-stones-removed-with-same-row-or-column\/\">Most Stones Removed with Same Row or Column<\/a><\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Thought<\/h2>\n\n\n\n<p>When I saw the question, I realized its a Union Find question &#8211; For any union, I can keep only one stone form it. Then it convert to a count how many unique union finds exist question.\u00a0<\/p>\n\n\n\n<p>So, only need to count all unique union find, and use all nodes to minus it.&nbsp;<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Code<\/h2>\n\n\n\n<pre class=\"wp-block-syntaxhighlighter-code brush: python; notranslate\">class Solution:\n    def removeStones(self, stones):\n        \"\"\"\n        :type stones: List[List[int]]\n        :rtype: int\n        \"\"\"\n        N = len(stones)\n        nodes = dict()\n        cols = collections.defaultdict(set)\n        rows = collections.defaultdict(set)\n        counter = set()\n        for x, y in stones: # pre process\n            nodes[(x,y)] = (x,y)\n            cols[x].add(y)\n            rows[y].add(x)\n        def find(x,y):\n            if nodes[(x,y)]!= (x,y):\n                nx,ny = find(*nodes[(x,y)])\n                nodes[(x,y)] = (nx,ny)\n            return nodes[(x,y)]\n        def union(x,y,x2,y2):\n            n_x , n_y = find(x,y)\n            nn_x, nn_y = find(x2,y2)\n            nodes[(nn_x,nn_y)] = (n_x, n_y)\n        for x, y in stones:\n            for y2 in cols[x]:\n                union(x,y,x,y2)\n            for x2 in rows[y]:\n                union(x,y, x2,y)\n        maxx = 0\n        for x,y in stones:\n            r_x, r_y = find(x,y)\n            counter.add((r_x,r_y))\n        return N - len(counter) <\/pre>\n\n\n\n<h2 class=\"wp-block-heading\">Runtime<\/h2>\n\n\n\n<p>Time: O(n^2)<\/p>\n\n\n\n<p>Space: O(n)<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Link:&nbsp;Most Stones Removed with Same Row or Column Thought When I saw the question, I realized its a Union Find [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center 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