\uc548\ub155\ud558\uc138\uc694! \uc774\ubc88 \uae00\uc5d0\uc11c\ub294 C++\uc744 \uc774\uc6a9\ud55c \ucf54\ub529\ud14c\uc2a4\ud2b8 \ubb38\uc81c \uc911 \ud558\ub098\uc778 “K\ubc88\uc9f8 \uc218 \uad6c\ud558\uae30”\uc5d0 \ub300\ud574 \ub2e4\ub904\ubcf4\uaca0\uc2b5\ub2c8\ub2e4. \ucfe0\ud3f0 \ud53d\uc5c5\uacfc \uac19\uc774 \uc2e4\uc0dd\ud65c\uc5d0\uc11c\ub3c4 \ud55c \ubc88\ucbe4\uc740 \uace0\ubbfc\ud574\ubcf8 K\ubc88\uc9f8 \uc218 \uad6c\ud558\uae30 \ubb38\uc81c\ub294 \uc54c\uace0\ub9ac\uc998 \ubb38\uc81c\ud480\uc774\uc5d0\uc11c \uc790\uc8fc \uc811\ud560 \uc218 \uc788\ub294 \ubb38\uc81c \uc911 \ud558\ub098\uc785\ub2c8\ub2e4. \uc774\ubc88 \ud3ec\uc2a4\ud2b8\uc5d0\uc11c\ub294 \ubb38\uc81c \uc815\uc758\ubd80\ud130 \ud480\uc774 \uacfc\uc815, C++ \ucf54\ub4dc \uad6c\ud604\uae4c\uc9c0 \uc0c1\uc138\ud788 \uc124\uba85\ud558\uaca0\uc2b5\ub2c8\ub2e4.<\/p>\n
\uc8fc\uc5b4\uc9c4 \uc815\uc218 \ubc30\uc5f4\uc774 \uc788\uace0, \uc774 \ubc30\uc5f4\uc5d0\uc11c K\ubc88\uc9f8\ub85c \uc791\uc740 \uc218\ub97c \ucc3e\ub294 \ubb38\uc81c\uc785\ub2c8\ub2e4. \uc5ec\uae30\uc11c K\ub294 1\ubd80\ud130 \uc2dc\uc791\ud558\ub294 \uc815\uc218\ub85c, \uccab \ubc88\uc9f8\ub85c \uc791\uc740 \uc218, \ub450 \ubc88\uc9f8\ub85c \uc791\uc740 \uc218, …\uc758 \uc758\ubbf8\ub97c \uac16\uc2b5\ub2c8\ub2e4.<\/p>\n
\uc608\ub97c \ub4e4\uc5b4, \ub2e4\uc74c\uacfc \uac19\uc740 \uc785\ub825\uc744 \uace0\ub824\ud574 \ubd05\uc2dc\ub2e4:<\/p>\n
\n\ubc30\uc5f4: [3, 1, 2, 4, 5]\nK: 3\n<\/pre>\n\uc8fc\uc5b4\uc9c4 \ubc30\uc5f4\uc5d0\uc11c 3\ubc88\uc9f8\ub85c \uc791\uc740 \uc218\ub294 3\uc785\ub2c8\ub2e4. \ub530\ub77c\uc11c \uc774 \uacbd\uc6b0\uc758 \uc815\ub2f5\uc740 3\uc774 \ub429\ub2c8\ub2e4.<\/p>\n
\uc785\ub825 \ud615\uc2dd<\/h3>\n
\n
- \uccab \ubc88\uc9f8 \uc904: \ubc30\uc5f4\uc758 \uae38\uc774 N (1 <= N <= 100,000)<\/li>\n
- \ub450 \ubc88\uc9f8 \uc904: \uc815\uc218 \ubc30\uc5f4 A (1 <= A[i] <= 10^9)<\/li>\n
- \uc138 \ubc88\uc9f8 \uc904: \uc815\uc218 K (1 <= K <= N)<\/li>\n<\/ul>\n
\ucd9c\ub825 \ud615\uc2dd<\/h3>\n
K\ubc88\uc9f8\ub85c \uc791\uc740 \uc218\ub97c \ucd9c\ub825\ud569\ub2c8\ub2e4.<\/p>\n
\ubb38\uc81c \ud480\uc774 \uacc4\ud68d<\/h2>\n
\uc774 \ubb38\uc81c\ub97c \ud574\uacb0\ud558\uae30 \uc704\ud574 \uc0ac\uc6a9\ud560 \uc218 \uc788\ub294 \uba87 \uac00\uc9c0 \uc54c\uace0\ub9ac\uc998\uc744 \uc0dd\uac01\ud574 \ubcfc \uc218 \uc788\uc2b5\ub2c8\ub2e4.<\/p>\n
\n
- \uc815\ub82c: \ubc30\uc5f4\uc744 \uc815\ub82c\ud55c \ud6c4 K\ubc88\uc9f8 \uc778\ub371\uc2a4\ub97c \ubc18\ud658\ud569\ub2c8\ub2e4.<\/li>\n
- \ucd5c\uc18c\ud799 \uc0ac\uc6a9: \ud799\uc744 \uc0ac\uc6a9\ud574\uc11c K\ubc88\uc9f8\ub85c \uc791\uc740 \uc218\ub97c \ucc3e\uc544\ub0bc \uc218 \uc788\uc2b5\ub2c8\ub2e4.<\/li>\n
- \ud035 \uc120\ud0dd \uc54c\uace0\ub9ac\uc998: \ud3c9\uade0 O(N) \uc2dc\uac04\ubcf5\uc7a1\ub3c4\ub85c K\ubc88\uc9f8 \uc218\ub97c \ucc3e\uc744 \uc218 \uc788\ub294 \uc54c\uace0\ub9ac\uc998\uc785\ub2c8\ub2e4.<\/li>\n<\/ul>\n
\uc5ec\uae30\uc11c\ub294 \uac00\uc7a5 \uc9c1\uad00\uc801\uc774\uace0 \uc774\ud574\ud558\uae30 \uc26c\uc6b4 \ubc29\ubc95\uc778 \ubc30\uc5f4 \uc815\ub82c\uc744 \uc0ac\uc6a9\ud55c \ud480\uc774\ub97c \uad6c\ud604\ud574 \ubcf4\uaca0\uc2b5\ub2c8\ub2e4.<\/p>\n
\uad6c\ud604\ud558\uae30<\/h2>\n
\uba3c\uc800 C++\uc758
vector<\/code>\ub97c \uc0ac\uc6a9\ud558\uc5ec \ubc30\uc5f4\uc744 \uc785\ub825\ubc1b\uace0,sort()<\/code> \ud568\uc218\ub97c \uc774\uc6a9\ud574 \uc815\ub82c\ud558\uaca0\uc2b5\ub2c8\ub2e4. \uadf8 \ud6c4, K\ubc88\uc9f8 \uc218\ub97c \ucd9c\ub825\ud558\ub294 \ubc29\uc2dd\uc73c\ub85c \ud504\ub85c\uadf8\ub7a8\uc744 \uad6c\uc131\ud558\uaca0\uc2b5\ub2c8\ub2e4.<\/p>\n\ucf54\ub4dc \uad6c\ud604<\/h3>\n
\n#include\n#include \n#include \/\/ sort()\uc758 \uc0ac\uc6a9\uc744 \uc704\ud574 include\nusing namespace std;\n\nint main() {\n int N, K;\n \n \/\/ \ubc30\uc5f4\uc758 \ud06c\uae30 N \uc785\ub825\n cout << \"\ubc30\uc5f4\uc758 \uae38\uc774 N\uc744 \uc785\ub825\ud558\uc138\uc694: \";\n cin >> N;\n\n vector A(N);\n \n \/\/ \ubc30\uc5f4 A \uc785\ub825\n cout << \"\uc815\uc218 \ubc30\uc5f4 A\ub97c \uc785\ub825\ud558\uc138\uc694 (\ub744\uc5b4\uc4f0\uae30\ub85c \uad6c\ubd84): \";\n for(int i = 0; i < N; i++) {\n cin >> A[i];\n }\n \n \/\/ K \uac12 \uc785\ub825\n cout << \"K \uac12\uc744 \uc785\ub825\ud558\uc138\uc694: \";\n cin >> K;\n\n \/\/ \ubc30\uc5f4 \uc815\ub82c\n sort(A.begin(), A.end());\n\n \/\/ K\ubc88\uc9f8 \uc218 \ucd9c\ub825 (\uc778\ub371\uc2a4\ub294 K-1)\n cout << K << \"\ubc88\uc9f8 \uc218\ub294: \" << A[K - 1] << endl;\n\n return 0;\n}\n<\/int><\/algorithm><\/vector><\/iostream><\/pre>\n \ucf54\ub4dc \uc124\uba85<\/h2>\n
\uc774 \ucf54\ub4dc\ub294 \ub2e4\uc74c\uacfc \uac19\uc740 \ud750\ub984\uc73c\ub85c \ub3d9\uc791\ud569\ub2c8\ub2e4:<\/p>\n
\n
- \uc0ac\uc6a9\uc790\ub85c\ubd80\ud130 \ubc30\uc5f4\uc758 \uae38\uc774 N\uc744 \uc785\ub825\ubc1b\uc2b5\ub2c8\ub2e4.<\/li>\n
- N \uae38\uc774\uc758 \uc815\uc218 \ud615 \ubca1\ud130 A\ub97c \uc0dd\uc131\ud569\ub2c8\ub2e4.<\/li>\n
- \uc0ac\uc6a9\uc790\ub85c\ubd80\ud130 \ubc30\uc5f4 A\uc758 \uc6d0\uc18c\ub97c \uc785\ub825\ubc1b\uc2b5\ub2c8\ub2e4.<\/li>\n
- K \uac12\uc744 \uc785\ub825\ubc1b\uc2b5\ub2c8\ub2e4.<\/li>\n
- \ubc30\uc5f4 A\ub97c \uc624\ub984\ucc28\uc21c\uc73c\ub85c \uc815\ub82c\ud569\ub2c8\ub2e4.<\/li>\n
- K\ubc88\uc9f8 \uc218\ub97c \ucd9c\ub825\ud569\ub2c8\ub2e4. C++\uc5d0\uc11c\ub294 \uc778\ub371\uc2a4\uac00 0\ubd80\ud130 \uc2dc\uc791\ud558\ubbc0\ub85c K-1\uc744 \uc0ac\uc6a9\ud574\uc57c \ud569\ub2c8\ub2e4.<\/li>\n<\/ol>\n
\ucf54\ub4dc \ubd84\uc11d<\/h2>\n
\ubb38\uc81c\uc758 \uc785\ub825\uc740 \ucd5c\ub300 100,000\uac1c\ub85c, \ucd5c\uc545\uc758 \uacbd\uc6b0
O(N log N)<\/code>\uc758 \uc2dc\uac04\ubcf5\uc7a1\ub3c4\ub97c \uac00\uc9c4 \uc815\ub82c\uc744 \uc218\ud589\ud558\uac8c \ub429\ub2c8\ub2e4. \uc815\ub82c \ud6c4\uc5d0\ub294 K\ubc88\uc9f8 \uc218\ub97c O(1) \uc2dc\uac04\uc5d0 \ucc3e\uc744 \uc218 \uc788\uc73c\ubbc0\ub85c, \uc804\uccb4 \uc2dc\uac04\ubcf5\uc7a1\ub3c4\ub294O(N log N)<\/code>\uc785\ub2c8\ub2e4. \uc774\ub294 \uc8fc\uc5b4\uc9c4 \uc2dc\uac04 \uc81c\ud55c \ub0b4\uc5d0 \ucda9\ubd84\ud788 \ud574\uacb0\ud560 \uc218 \uc788\ub294 \ubcf5\uc7a1\ub3c4\uc785\ub2c8\ub2e4.<\/p>\n\ud14c\uc2a4\ud2b8 \ucf00\uc774\uc2a4<\/h2>\n
\uc704 \ucf54\ub4dc\ub97c \uac80\uc99d\ud558\uae30 \uc704\ud574 \uba87 \uac00\uc9c0 \ud14c\uc2a4\ud2b8 \ucf00\uc774\uc2a4\ub97c \uace0\ub824\ud574 \ubcf4\uaca0\uc2b5\ub2c8\ub2e4:<\/p>\n
\ud14c\uc2a4\ud2b8 \ucf00\uc774\uc2a4 1<\/h3>\n
\n\uc785\ub825:\n5\n3 1 2 4 5\n3\n\ucd9c\ub825:\n3\ubc88\uc9f8 \uc218\ub294: 3\n<\/pre>\n\ud14c\uc2a4\ud2b8 \ucf00\uc774\uc2a4 2<\/h3>\n
\n\uc785\ub825:\n10\n10 9 8 7 6 5 4 3 2 1\n5\n\ucd9c\ub825:\n5\ubc88\uc9f8 \uc218\ub294: 5\n<\/pre>\n\ud14c\uc2a4\ud2b8 \ucf00\uc774\uc2a4 3<\/h3>\n
\n\uc785\ub825:\n5\n1 10000 500 999 1000\n2\n\ucd9c\ub825:\n2\ubc88\uc9f8 \uc218\ub294: 500\n<\/pre>\n\uacb0\uacfc \ubc0f \ucd5c\uc801\ud654<\/h2>\n
\uae30\ubcf8\uc801\uc778 \ud480\uc774\ub97c \uad6c\ud604\ud574 \ubcf4\uc558\uc2b5\ub2c8\ub2e4. \uc815\ub82c\uc744 \uc0ac\uc6a9\ud55c \ubc29\ubc95\uc740 \uc9c1\uad00\uc801\uc774\uba70 \uad6c\ud604\uc774 \uc6a9\uc774\ud558\uc9c0\ub9cc, \ubc30\uc5f4\uc758 \ud06c\uae30\uac00 \ub9e4\uc6b0 \ud074 \uacbd\uc6b0 \ub2e4\ub978 \ubc29\ubc95\uc774 \ud544\uc694\ud560 \uc218 \uc788\uc2b5\ub2c8\ub2e4. \uc608\ub97c \ub4e4\uc5b4, \ud035 \uc120\ud0dd \uc54c\uace0\ub9ac\uc998\uc744 \uc0ac\uc6a9\ud558\ub294 \ubc29\ubc95\uc774 \uc788\uc2b5\ub2c8\ub2e4. \ud035 \uc120\ud0dd \uc54c\uace0\ub9ac\uc998\uc740 \ud3c9\uade0\uc801\uc73c\ub85c O(N)\uc758 \uc131\ub2a5\uc744 \uac00\uc9c0\uba70, \uba54\ubaa8\ub9ac\uac00 \uc81c\ud55c\ub41c \uacbd\uc6b0 \uc720\uc6a9\ud558\uac8c \uc0ac\uc6a9\ub420 \uc218 \uc788\uc2b5\ub2c8\ub2e4.<\/p>\n
\ud035 \uc120\ud0dd \uc54c\uace0\ub9ac\uc998 \uac1c\uc694<\/h3>\n
\ud035 \uc120\ud0dd \uc54c\uace0\ub9ac\uc998\uc740 \ubd84\ud560 \uc815\ubcf5 \uc54c\uace0\ub9ac\uc998\uc758 \uc77c\uc885\uc73c\ub85c, \ub79c\ub364 \ud53c\ubc97\uc744 \uc120\ud0dd\ud558\uc5ec \ubc30\uc5f4\uc744 \ub450 \ubd80\ubd84\uc73c\ub85c \ub098\ub204\uace0 K\ubc88\uc9f8 \uc218\uac00 \uc5b4\ub5a4 \ubd80\ubd84\uc5d0 \uc788\ub294\uc9c0\ub97c \ud310\ubcc4\ud558\uc5ec \ud574\ub2f9 \ubd80\ubd84\ub9cc \uacc4\uc18d \ucc3e\ub294 \ubc29\ubc95\uc785\ub2c8\ub2e4. \ub9e4\uc6b0 \ud070 \ubc30\uc5f4\uc5d0\uc11c\ub3c4 \ube60\ub974\uac8c K\ubc88\uc9f8 \uc218\ub97c \ucc3e\uc744 \uc218 \uc788\uc2b5\ub2c8\ub2e4.<\/p>\n
\ud035 \uc120\ud0dd \uad6c\ud604 \uc608\uc2dc<\/h3>\n
\n#include <iostream>\n#include <vector>\n#include <cstdlib> \/\/ rand() \ud568\uc218\ub97c \uc704\ud574\nusing namespace std;\n\n\/\/ \ubc30\uc5f4\uc5d0\uc11c K\ubc88\uc9f8 \uc218\ub97c \ucc3e\ub294 \ud035 \uc120\ud0dd \uc54c\uace0\ub9ac\uc998\nint quickSelect(vector& A, int left, int right, int K) {\n if (left == right) return A[left];\n\n int pivotIndex = left + rand() % (right - left);\n int pivotValue = A[pivotIndex];\n\n \/\/ \ud53c\ubc97\uc744 \ubc30\uc5f4\uc758 \ub9e8 \ub05d\uc73c\ub85c \uc774\ub3d9\n swap(A[pivotIndex], A[right]);\n int storeIndex = left;\n\n for (int i = left; i < right; i++) {\n if (A[i] < pivotValue) {\n swap(A[storeIndex], A[i]);\n storeIndex++;\n }\n }\n\n \/\/ \ud53c\ubc97\uc744 \uc790\uc2e0\uc758 \uc704\uce58\ub85c \uc774\ub3d9\n swap(A[storeIndex], A[right]);\n\n if (K == storeIndex) return A[K];\n else if (K < storeIndex) return quickSelect(A, left, storeIndex - 1, K);\n else return quickSelect(A, storeIndex + 1, right, K);\n}\n\nint main() {\n int N, K;\n\n cout << \"\ubc30\uc5f4\uc758 \uae38\uc774 N\uc744 \uc785\ub825\ud558\uc138\uc694: \";\n cin >> N;\n\n vector A(N);\n \n cout << \"\uc815\uc218 \ubc30\uc5f4 A\ub97c \uc785\ub825\ud558\uc138\uc694 (\ub744\uc5b4\uc4f0\uae30\ub85c \uad6c\ubd84): \";\n for(int i = 0; i < N; i++) {\n cin >> A[i];\n }\n\n cout << \"K \uac12\uc744 \uc785\ub825\ud558\uc138\uc694: \";\n cin >> K;\n\n int result = quickSelect(A, 0, N - 1, K - 1);\n cout << K << \"\ubc88\uc9f8 \uc218\ub294: \" << result << endl;\n\n return 0;\n}\n<\/int><\/int><\/pre>\n \ub9c8\ubb34\ub9ac<\/h2>\n
\uc624\ub298\uc740 C++\uc744 \uc774\uc6a9\ud558\uc5ec K\ubc88\uc9f8 \uc218\ub97c \ucc3e\ub294 \ubb38\uc81c\ub97c \ud574\uacb0\ud558\ub294 \ubc29\ubc95\uc5d0 \ub300\ud574 \uc54c\uc544\ubcf4\uc558\uc2b5\ub2c8\ub2e4. \uae30\ubcf8\uc801\uc778 \ubc29\ubc95\uc73c\ub85c\ub294 \ubc30\uc5f4\uc744 \uc815\ub82c\ud558\uc5ec K\ubc88\uc9f8 \uc218\ub97c \ucc3e\ub294 \ubc29\ubc95\uc744 \uad6c\ud604\ud558\uc600\uace0, \ub354 \ud6a8\uc728\uc801\uc778 \ubc29\ubc95\uc73c\ub85c \ud035 \uc120\ud0dd \uc54c\uace0\ub9ac\uc998\uc5d0 \ub300\ud574\uc11c\ub3c4 \uac04\ub7b5\ud788 \uc124\uba85\ub4dc\ub838\uc2b5\ub2c8\ub2e4. \uc774\ub7ec\ud55c \ubb38\uc81c\ub4e4\uc740 \ucf54\ub529 \ud14c\uc2a4\ud2b8\uc5d0\uc11c \uc790\uc8fc \ucd9c\uc81c\ub418\ubbc0\ub85c \ubc18\ubcf5\uc801\uc73c\ub85c \ud559\uc2b5\ud574 \ub450\ub294 \uac83\uc774 \uc88b\uc2b5\ub2c8\ub2e4. \uc774 \ubb38\uc81c\ub97c \ud1b5\ud574 \uc54c\uace0\ub9ac\uc998\uc758 \uae30\ucd08\uc801\uc778 \uc774\ud574\uc640 C++ \ud504\ub85c\uadf8\ub798\ubc0d \ub2a5\ub825\uc744 \ud0a4\uc6b0\ub294 \ub370 \ub3c4\uc6c0\uc774 \ub418\uae38 \ubc14\ub78d\ub2c8\ub2e4.<\/p>\n
\ub3c5\uc11c \uac10\uc0ac\ud569\ub2c8\ub2e4! \ucd94\uac00\uc801\uc778 \uc9c8\ubb38\uc774 \uc788\uc73c\uc2dc\uba74 \ub313\uae00\ub85c \ub0a8\uaca8\uc8fc\uc138\uc694.<\/p>\n
<\/body><\/p>\n","protected":false},"excerpt":{"rendered":"