{"id":1849,"date":"2022-01-12T16:07:02","date_gmt":"2022-01-12T08:07:02","guid":{"rendered":"http:\/\/139.9.1.231\/?p=1849"},"modified":"2022-01-12T16:07:03","modified_gmt":"2022-01-12T08:07:03","slug":"leetcodeday16","status":"publish","type":"post","link":"http:\/\/139.9.1.231\/index.php\/2022\/01\/12\/leetcodeday16\/","title":{"rendered":"leetcodeday16 —\u6700\u63a5\u8fd1\u7684\u4e09\u6570\u4e4b\u548c"},"content":{"rendered":"\n

\u8fd9\u4e2a\u601d\u8def\u548c\u4e0a\u4e00\u4e2a\u9898\u5dee\u4e0d\u591a\uff0c\u4e0d\u8fc7\u7b80\u5355\u4e00\u4e9b\uff0c\u53ea\u9700\u8981\u627e\u51fa\u4e09\u4e2a\u6570\u7684\u548c\u3002\u56e0\u6b64\u7ed9\u51fa\u5b98\u65b9\u7b54\u6848\u3002<\/p>\n\n\n\n

\u7ed9\u4f60\u4e00\u4e2a\u957f\u5ea6\u4e3a n<\/code> \u7684\u6574\u6570\u6570\u7ec4 nums<\/code>\u548c \u4e00\u4e2a\u76ee\u6807\u503c target<\/code>\u3002\u8bf7\u4f60\u4ece nums<\/code>\u4e2d\u9009\u51fa\u4e09\u4e2a\u6574\u6570\uff0c\u4f7f\u5b83\u4eec\u7684\u548c\u4e0e target<\/code> \u6700\u63a5\u8fd1\u3002<\/p>\n\n\n\n

\u8fd4\u56de\u8fd9\u4e09\u4e2a\u6570\u7684\u548c\u3002<\/p>\n\n\n\n

\u5047\u5b9a\u6bcf\u7ec4\u8f93\u5165\u53ea\u5b58\u5728\u6070\u597d\u4e00\u4e2a\u89e3\u3002<\/p>\n\n\n\n

\u793a\u4f8b 1\uff1a<\/strong><\/p>\n\n\n\n

\u8f93\u5165\uff1a<\/strong>nums = [-1,2,1,-4], target = 1\n\u8f93\u51fa\uff1a<\/strong>2\n\u89e3\u91ca\uff1a<\/strong>\u4e0e target \u6700\u63a5\u8fd1\u7684\u548c\u662f 2 (-1 + 2 + 1 = 2) \u3002<\/code><\/pre>\n\n\n\n
\u6392\u5e8f + \u53cc\u6307\u9488
\u601d\u8def\u4e0e\u7b97\u6cd5<\/p>\n\n\n\n
\u9898\u76ee\u8981\u6c42\u627e\u5230\u4e0e\u76ee\u6807\u503c target \u6700\u63a5\u8fd1\u7684\u4e09\u5143\u7ec4\uff0c\u8fd9\u91cc\u7684\u300c\u6700\u63a5\u8fd1\u300d\u5373\u4e3a\u5dee\u503c\u7684\u7edd\u5bf9\u503c\u6700\u5c0f\u3002\u6211\u4eec\u53ef\u4ee5\u8003\u8651\u76f4\u63a5\u4f7f\u7528\u4e09\u91cd\u5faa\u73af\u679a\u4e3e\u4e09\u5143\u7ec4\uff0c\u627e\u51fa\u4e0e\u76ee\u6807\u503c\u6700\u63a5\u8fd1\u7684\u4f5c\u4e3a\u7b54\u6848\uff0c\u65f6\u95f4\u590d\u6742\u5ea6\u4e3a O(N^3)\u3002\u7136\u800c\u672c\u9898\u7684 N \u6700\u5927\u4e3a 1000\uff0c\u4f1a\u8d85\u51fa\u65f6\u95f4\u9650\u5236\u3002<\/p>\n\n\n\n
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\u5982\u679c a+b+c\u2265target\uff0c\u90a3\u4e48\u5c31\u5c06 p_c\u5411\u5de6\u79fb\u52a8\u4e00\u4e2a\u4f4d\u7f6e\uff1b<\/p>\n\n\n\n
\u5982\u679c a+b+c<target\uff0c\u90a3\u4e48\u5c31\u5c06 p_b\u5411\u53f3\u79fb\u52a8\u4e00\u4e2a\u4f4d\u7f6e\u3002\u8fd9\u662f\u4e3a\u4ec0\u4e48\u5462\uff1f\u6211\u4eec\u5bf9 a+b+c\u2265target \u7684\u60c5\u51b5\u8fdb\u884c\u4e00\u4e2a\u8be6\u7ec6\u7684\u5206\u6790\uff1a<\/p>\n\n\n\n
\u5982\u679c a+b+c\u2265target\uff0c\u5e76\u4e14\u6211\u4eec\u77e5\u9053 p_b\u5230 p_c\u8fd9\u4e2a\u8303\u56f4\u5185\u7684\u6240\u6709\u6570\u662f\u6309\u7167\u5347\u5e8f\u6392\u5e8f\u7684\uff0c\u90a3\u4e48\u5982\u679c p_c\u4e0d\u53d8\u800c p_b\u5411\u53f3\u79fb\u52a8\uff0c\u90a3\u4e48 a+b+c \u7684\u503c\u5c31\u4f1a\u4e0d\u65ad\u5730\u589e\u52a0\uff0c\u663e\u7136\u5c31\u4e0d\u4f1a\u6210\u4e3a\u6700\u63a5\u8fd1 target \u7684\u503c\u4e86\u3002\u56e0\u6b64\uff0c\u6211\u4eec\u53ef\u4ee5\u77e5\u9053\u5728\u56fa\u5b9a\u4e86 p_c\u7684\u60c5\u51b5\u4e0b\uff0c\u6b64\u65f6\u7684 p_b\u5c31\u53ef\u4ee5\u5f97\u5230\u4e00\u4e2a\u6700\u63a5\u8fd1target \u7684\u503c\uff0c\u90a3\u4e48\u6211\u4eec\u4ee5\u540e\u5c31\u4e0d\u7528\u518d\u8003\u8651 p_c\u4e86\uff0c\u5c31\u53ef\u4ee5\u5c06 p_c\u5411\u5de6\u79fb\u52a8\u4e00\u4e2a\u4f4d\u7f6e\u3002<\/p>\n\n\n\n
\u540c\u6837\u5730\uff0c\u5728 a+b+c<target \u65f6\uff1a<\/p>\n\n\n\n
\u5982\u679c a+b+c<target\uff0c\u5e76\u4e14\u6211\u4eec\u77e5\u9053 p_b\u5230 p_c\u8fd9\u4e2a\u8303\u56f4\u5185\u7684\u6240\u6709\u6570\u662f\u6309\u7167\u5347\u5e8f\u6392\u5e8f\u7684\uff0c\u90a3\u4e48\u5982\u679c p_b\u4e0d\u53d8\u800c p_c\u5411\u5de6\u79fb\u52a8\uff0c\u90a3\u4e48 a+b+c \u7684\u503c\u5c31\u4f1a\u4e0d\u65ad\u5730\u51cf\u5c0f\uff0c\u663e\u7136\u5c31\u4e0d\u4f1a\u6210\u4e3a\u6700\u63a5\u8fd1 target \u7684\u503c\u4e86\u3002\u56e0\u6b64\uff0c\u6211\u4eec\u53ef\u4ee5\u77e5\u9053\u5728\u56fa\u5b9a\u4e86 p_b\u7684\u60c5\u51b5\u4e0b\uff0c\u6b64\u65f6\u7684 p_cp\u5c31\u53ef\u4ee5\u5f97\u5230\u4e00\u4e2a\u6700\u63a5\u8fd1 target \u7684\u503c\uff0c\u90a3\u4e48\u6211\u4eec\u4ee5\u540e\u5c31\u4e0d\u7528\u518d\u8003\u8651 p_b\u4e86\uff0c\u5c31\u53ef\u4ee5\u5c06 p_b\u5411\u53f3\u79fb\u52a8\u4e00\u4e2a\u4f4d\u7f6e\u3002\u5b9e\u9645\u4e0a\uff0cp_b\u548c p_c\u5c31\u8868\u793a\u4e86\u6211\u4eec\u5f53\u524d\u53ef\u4ee5\u9009\u62e9\u7684\u6570\u7684\u8303\u56f4\uff0c\u800c\u6bcf\u4e00\u6b21\u679a\u4e3e\u7684\u8fc7\u7a0b\u4e2d\uff0c\u6211\u4eec\u5c1d\u8bd5\u8fb9\u754c\u4e0a\u7684\u4e24\u4e2a\u5143\u7d20\uff0c\u6839\u636e\u5b83\u4eec\u4e0e target \u7684\u503c\u7684\u5173\u7cfb\uff0c\u9009\u62e9\u300c\u629b\u5f03\u300d\u5de6\u8fb9\u754c\u7684\u5143\u7d20\u8fd8\u662f\u53f3\u8fb9\u754c\u7684\u5143\u7d20\uff0c\u4ece\u800c\u51cf\u5c11\u4e86\u679a\u4e3e\u7684\u8303\u56f4\u3002\u8fd9\u79cd\u601d\u8def\u4e0e\u76db\u6700\u591a\u6c34\u7684\u5bb9\u5668 \u4e2d\u7684\u53cc\u6307\u9488\u89e3\u6cd5\u4e5f\u662f\u7c7b\u4f3c\u7684\u3002<\/p>\n\n\n\n
\u5c0f\u4f18\u5316<\/p>\n\n\n\n
\u672c\u9898\u4e5f\u6709\u4e00\u4e9b\u53ef\u4ee5\u51cf\u5c11\u8fd0\u884c\u65f6\u95f4\uff08\u4f46\u4e0d\u4f1a\u51cf\u5c11\u65f6\u95f4\u590d\u6742\u5ea6\uff09\u7684\u5c0f\u4f18\u5316\u3002\u5f53\u6211\u4eec\u679a\u4e3e\u5230\u6070\u597d\u7b49\u4e8etarget \u7684 a+b+c\u65f6\uff0c\u53ef\u4ee5\u76f4\u63a5\u8fd4\u56de target \u4f5c\u4e3a\u7b54\u6848\uff0c\u56e0\u4e3a\u4e0d\u4f1a\u6709\u518d\u6bd4\u8fd9\u4e2a\u66f4\u63a5\u8fd1\u7684\u503c\u4e86\u3002<\/p>\n\n\n\n
\u53e6\u4e00\u4e2a\u4f18\u5316\u4e0e \u4e09\u6570\u4e4b\u548c\u7684\u5b98\u65b9\u9898\u89e3 \u4e2d\u63d0\u5230\u7684\u7c7b\u4f3c\u3002\u5f53\u6211\u4eec\u679a\u4e3e a, b, c\u4e2d\u4efb\u610f\u5143\u7d20\u5e76\u79fb\u52a8\u6307\u9488\u65f6\uff0c\u53ef\u4ee5\u76f4\u63a5\u5c06\u5176\u79fb\u52a8\u5230\u4e0b\u4e00\u4e2a\u4e0e\u8fd9\u6b21\u679a\u4e3e\u5230\u7684\u4e0d\u76f8\u540c\u7684\u5143\u7d20\uff0c\u51cf\u5c11\u679a\u4e3e\u7684\u6b21\u6570\u3002<\/p>\n\n\n\n
class Solution:\n    def threeSumClosest(self, nums: List[int], target: int) -> int:\n        nums.sort()\n        n = len(nums)\n        best = 10**7\n        \n        # \u6839\u636e\u5dee\u503c\u7684\u7edd\u5bf9\u503c\u6765\u66f4\u65b0\u7b54\u6848\n        def update(cur):\n            nonlocal best\n            if abs(cur - target) < abs(best - target):\n                best = cur\n        \n        # \u679a\u4e3e a\n        for i in range(n):\n            # \u4fdd\u8bc1\u548c\u4e0a\u4e00\u6b21\u679a\u4e3e\u7684\u5143\u7d20\u4e0d\u76f8\u7b49\n            if i > 0 and nums[i] == nums[i - 1]:\n                continue\n            # \u4f7f\u7528\u53cc\u6307\u9488\u679a\u4e3e b \u548c c\n            j, k = i + 1, n - 1\n            while j < k:\n                s = nums[i] + nums[j] + nums[k]\n                # \u5982\u679c\u548c\u4e3a target \u76f4\u63a5\u8fd4\u56de\u7b54\u6848\n                if s == target:\n                    return target\n                update(s)\n                if s > target:\n                    # \u5982\u679c\u548c\u5927\u4e8e target\uff0c\u79fb\u52a8 c \u5bf9\u5e94\u7684\u6307\u9488\n                    k0 = k - 1\n                    # \u79fb\u52a8\u5230\u4e0b\u4e00\u4e2a\u4e0d\u76f8\u7b49\u7684\u5143\u7d20\n                    while j < k0 and nums[k0] == nums[k]:\n                        k0 -= 1\n                    k = k0\n                else:\n                    # \u5982\u679c\u548c\u5c0f\u4e8e target\uff0c\u79fb\u52a8 b \u5bf9\u5e94\u7684\u6307\u9488\n                    j0 = j + 1\n                    # \u79fb\u52a8\u5230\u4e0b\u4e00\u4e2a\u4e0d\u76f8\u7b49\u7684\u5143\u7d20\n                    while j0 < k and nums[j0] == nums[j]:\n                        j0 += 1\n                    j = j0\n\n        return best\n<\/code><\/pre>\n\n\n\n
\"\"<\/figure><\/div>\n","protected":false},"excerpt":{"rendered":"
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