鍔ㄦ极绠楁硶姊崇悊
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鍦ㄦ锛岀壒鍒劅璋㈠皬澶曞绠楁硶锛岃鍘ㄧ殑绠楁硶灏忓眿绛夊師鍒涗綔鑰呭ぇ鐗涖€?/p>
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鏈枃鎽樿嚜銆?strong>灏忓銆戯紝鐐瑰嚮鍙湅鍘熸枃
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鏉ユ簮锛氬姏鎵ｏ紙LeetCode锛夈€佸墤鎸噊ffer11
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鏈変汉璇达紝鍍忔垜涓嬮潰杩欐牱涓€涓惊鐜笉灏盇浜嗗悧锛熻€屼笖鍑昏触鐜?00%锛岃繕鏈変粈涔堢煡璇嗙偣锛?/p>
濡傛灉浣犱篃杩欐牱鎯筹紝閭ｅ氨澶ч敊鐗归敊浜嗐€備笖鍚垜鎱㈡參閬撴潵~~~
閭ｄ箞鐤戦棶鏉ヤ簡锛屼负浠€涔堣繖鏍峰啓涓嶆槸鏈€浼樼殑鍛紵
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鍦ㄦ湁搴忔暟缁勪腑鏌ユ壘鏌愪釜鍏冪礌锛屼竴鑸緝濂界殑鏂规硶鏄簩鍒嗘硶锛屽洜涓轰簩鍒嗘硶鍙互灏嗗鏉傚害闄嶄负logN锛?/p>
閭ｄ箞鍦ㄤ簩鍒嗘硶涓紝涓€鑸細鏈夋瘮杈冨熀鍑嗗€硷紝涔熷氨鏄痶arget锛屾湁瑙勫畾鐨勮瘽锛屽氨鎸夌収瑙勫畾鏉ュ彇锛屾病鏈夌殑璇濅竴鑸寜鐓ф渶宸︿晶鎴栨渶鍙充晶锛堜篃鍙О涓哄乏鍙崇鍊硷級鍙栦负target锛岃繖鍦ㄥ乏绁炵殑绠楁硶璇鹃噷璁茶繃锛?/p>
鍦ㄨ繖閬撻鐩腑鏄病鏈夌洰鏍囧€肩殑锛岄偅涔堢敤涓棿鍊煎拰浣庨珮浣嶏紙宸﹀彸绔€硷級杩涜姣旇緝锛岀湅澶勪簬鍓嶅崐閮ㄥ垎鐨勬槸閫掑搴忓垪杩樻槸鍚庡崐閮ㄥ垎鐨勬槸閫掑搴忓垪锛堟棆杞暟缁勶紝姣斿璇?code>[4,5,6,7,8,1,2,3]鍓嶅崐閮ㄥ垎鏄€掑搴忓垪[4,5,6,7,8]锛屽悗鍗婇儴鍒嗛€掑搴忓垪[1,2,3]锛夛紝杩涜鎿嶄綔缂╁皬鑼冨洿銆傜劧鍚庨€掑綊鍦ㄦ柊鐨勮寖鍥村唴鍐嶆鍒╃敤璇ユ€濇兂杩涜鏌ユ壘銆?/p>
鍦ㄨ繖閲屾垜娣诲姞涓€涓皬鏍楀瓙锛屾柟渚垮ぇ瀹堕槄璇伙細
姣斿锛氭暟缁刐4,5,6,7,8,1,2,3]锛屾暟缁勯暱搴︿负7锛屼腑闂村厓绱犳槸鏁扮粍闀?7/2=3锛屾墍鍦ㄤ綅缃殑鍏冪礌涓?銆傞偅涔堬紝灏辫鏁扮粍灏辫鍒嗕负涓ら儴鍒哰4,5,6,7]锛孾8,1,2,3]锛屽墠闈㈢殑鏁扮粍涓洪€掑锛屼笉鐢ㄧ锛屽悗闈㈢殑涓洪潪閫掑锛屾墍浠ヤ笅涓€娆″氨鍦ㄥ彸渚ф暟缁勯噷缁х画鏌ユ壘锛岄偅涔堝乏绔€煎厓绱犲氨鍙樹负8锛屽彸绔€煎厓绱犱笉鍙樿繕鏄?銆傝繖绉嶆儏鍐靛氨鏄湪鍙充晶鏌ユ壘锛?/p>
鍚屾牱鐨勮繕鏈夊湪宸︿晶鏁扮粍鏌ユ壘锛?/p>
姣斿鏁扮粍[7,8,1,2,3,4,5,6]锛屾暟缁勯暱搴︿负7锛屼腑闂村厓绱犳槸鏁扮粍闀?7/2=3锛屾墍鍦ㄤ綅缃殑鍏冪礌涓?銆傞偅涔堬紝灏辫鏁扮粍灏辫鍒嗕负涓ら儴鍒哰7,8,1,2]锛孾3,4,5,6]锛屽墠闈㈢殑鏁扮粍涓洪潪閫掑锛屽悗闈㈢殑涓洪€掑锛屼笉鐢ㄧ锛屾墍浠ヤ笅涓€娆″氨鍦ㄥ乏渚ф暟缁勯噷缁х画鏌ユ壘锛岄偅涔堝彸绔厓绱犲€煎氨鍙樹负2锛屽乏绔€煎厓绱犱笉鍙樿繕鏄?銆?/p>
杩欓噷鎴戜滑鎶妕arget 鐪嬩綔鏄?span class="Apple-converted-space">宸︾鐐?/strong>锛屾潵杩涜鍒嗘瀽锛岄偅灏辫鍒嗘瀽浠ヤ笅涓夌鎯呭喌锛岀湅鏄惁鍙互杈惧埌涓婅堪鐨勭洰鏍?
- 鎯呭喌1锛屾暟缁勬槸[1,2,3,4,5],宸︾鐐筶eft鐨勬暟缁勪笅鏍囩瓑浜?锛屽彸绔偣right鏁扮粍涓嬫爣绛変簬4銆傛暟缁勬槸閫掑鏁扮粍锛屾病鏈夊彂鐢熸壄杞€傚張鍥犱负arr[left]<arr[right]锛屾墍浠ユ渶灏忓€煎氨鏄痑rr[left]锛?/li>
- 鎯呭喌2锛屾暟缁勬槸[4,5,6,7,8,1,2,3],宸︾鐐筶eft鐨勬暟缁勪笅鏍囩瓑浜?锛屽彸绔偣right鏁扮粍涓嬫爣绛変簬7銆俛rr[left] > arr[right]锛屽彂鐢熶簡鎵浆銆傚張
arr[mid] = 7 > arr[left] = 4锛?/code> target涔熷氨鏄痑rr[left]涓哄乏绔偣 4锛?span class="Apple-converted-space">arr[mid] > target锛堜篃灏辨槸arr[left]锛?/code>, 璇存槑[first ... mid] 閮芥槸 >= target(涔熷氨鏄痑rr[left]) 鐨勶紝鍥犱负鍘熷鏁扮粍鏄潪閫掑噺锛屾墍浠ュ彲浠ョ‘瀹氱瓟妗堜负 [mid+1...last]鍖洪棿,鎵€浠?span class="Apple-converted-space">left= mid + 1锛?/code>
[5 6 1 2 3 4] ,宸︾鐐筶eft鐨勬暟缁勪笅鏍囩瓑浜?锛屽彸绔偣鏁扮粍涓嬫爣绛変簬5,mid涓嬫爣鏄?銆?code>arr[mid] = 1 < arr[right]=4 锛宎rr[mid] 涓?1锛?target涓哄彸绔偣 4锛?span class="Apple-converted-space"> arr[mid] < target锛坅rr[right]锛?/code>, 璇存槑绛旀鑲畾涓嶅湪[mid+1...right]锛屼絾鏄痑rr[mid] 鏈夊彲鑳芥槸绛旀,鎵€浠ョ瓟妗堝湪[first, mid]鍖洪棿锛屾墍浠ight = mid;鎯呭喌4锛?code>arr[mid] 鏃㈢瓑浜巃rr[left]鍙堢瓑浜巃rr[right]锛岄渶瑕佺壒娈婂鐞嗐€傝繘琛?code>left++锛屽鏋?code>arr[left] < arr[right] 閭ｄ箞鐩存帴杩斿洖arr[left]銆?/span>
濡傛灉涓婅堪杩樻病鐪嬫噦锛岃鐪嬩笅闈㈢殑瑙ｆ瀽鍥撅細
浠rray = [4,5,6,7,8,1,2,3]涓轰緥锛氬０鏄庯細涓嬪浘涓殑high 鍜宺ight涓€鏍风殑鎰忔€濄€?/p>
array[mid] = 7 > array[left] = 4鏄?span style="color: rgba(255, 0, 0, 1)">绗簩绉?/strong>鎯呭喌锛岀敱浜庨€掑鏈€灏忓€煎彧鍙兘鍦╩id鐨勫彸渚у尯闂达紝鏁呮柊鐨勫弬鏁帮細 left = mid+1 = 3+1 =4锛沵id = (left + high)/2 = 锛?+7锛?2 = 5 銆傛柊鐨勫浘鐢诲涓嬶細
array[mid] = 5 < array[left] = 8鏄?span style="color: rgba(255, 0, 0, 1)">绗笁绉?/strong>鎯呭喌锛岀敱浜庨€掑鏈€灏忓€煎彧鍙兘鍦╩id鐨勫乏渚у尯闂达紙鍖呮嫭mid锛夛紝鏁呮柊鐨勫弬鏁帮細 high = mid = 5锛沵id = (left + high)/2 = 锛?+5锛?2 = 4 銆?/span>
鏂扮殑鍥剧敾濡備笅锛?/p>
姝ゆ椂锛宎rray[mid] = 8 < array[left] = 8鏄?strong>绗洓绉?/strong>鎯呭喌锛屾柊鐨勫弬鏁板涓嬶細 left = left + 1 = 4+1 = 5 锛屾鏃?left = high锛屾晠鎵惧埌鏈€灏忓€硷紝涔熷氨鏄痑rray[5] = 1锛岃烦鍑哄惊鐜粨鏉熴€傚叾瀹炴柊鐨勫浘锛屼篃鍙涓嬬湅寰咃細
绗洓绉嶆儏鍐碉紝鍗曠嫭灏唋eft++锛岀洰鐨勬槸涓轰簡闃叉鍍廩2,0,2,2,2]绫讳技浜庤繖鏍风殑鏁扮粍鍑虹幇銆?/p>
濡傛灉鍍忚繖鏍风殑鏁扮粍锛岄偅涔堬紝鏍规嵁鍓嶈堪锛屼竴寮€濮媋rray[left] = array[mid] 鐨勶紝鍓嶄笁绉嶆儏鍐甸兘涓嶇鍚堛€傛墍浠ラ渶瑕佺壒娈婂鐞嗭紝灏辨槸绗洓绉嶃€?/p>
鍏跺疄濂藉ソ鎯充竴鎯筹紝绗簩绉嶆槸array[left] < array[mid] 锛岀涓夌鏄痑rray[left] > array[mid] 锛屾墍浠ヨ偗瀹氳繕鏈変竴绉嶆槸array[left] = array[mid]銆備絾杩欎釜鏃跺€欎綘灏变笉鑳藉垽鏂渶灏忓€兼槸鍦ㄥ乏鍖洪棿杩樻槸鍙冲尯闂淬€傛瘮濡傦細鏁扮粍[2,0,2,2,2]涓紝鏈€灏忓€?灏辨槸鍦ㄥ乏鍖洪棿锛涙暟缁刐2,2,2,2,2,0,2,2]涓紝鏈€灏忓€?灏辨槸鍦ㄥ彸鍖洪棿鍐呫€傛墍浠ワ紝涓轰簡纭畾鏄湪鍝竴涓尯闂村唴锛屾垜浠彧濂藉皢left+1锛岃繖鏍锋柊鐨勬暟缁勪篃缂╁皬浜嗭紝灏卞彲浠ョ户缁瘮瀵癸紝缁х画鍒ゆ柇鏂扮殑array[left] 鍜宎rray[mid] 鐨勫ぇ灏忔潵纭畾鏈€灏忓€煎湪鍝竴渚с€傚師鏂囦腑鍏充簬杩欎竴鐐硅繕鏈夊浘鐢伙紝鎴戝湪杩欓噷灏变笉閲嶅鍙欒堪浜嗭紝涓嶆噦寰楀彲浠ョЩ姝ワ紝椤哄甫鍏虫敞涓€娉㈠師鍗氫富锛屽搱鍝堝搱~~~
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