leetcode姣忔棩涓€棰樼郴鍒?鍏氦璺嚎

Posted 2021-09-04 鍒樼函鑹疄鍦ㄦ槸澶偉

leetcode-815-鍏氦璺嚎

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[鍗氬閾炬帴]

鑿滒煇旂殑瀛︿範涔嬭矾

鎺橀噾棣栭〉

[棰樼洰鎻忚堪]

缁欎綘涓€涓暟缁?routes 锛岃〃绀轰竴绯诲垪鍏氦绾胯矾锛屽叾涓瘡涓?routes[i] 琛ㄧず涓€鏉″叕浜ょ嚎璺紝绗?i 杈嗗叕浜よ溅灏嗕細鍦ㄤ笂闈㈠惊鐜椹躲€?


 渚嬪锛岃矾绾?routes[0] = [1, 5, 7] 琛ㄧず绗?0 杈嗗叕浜よ溅浼氫竴鐩存寜搴忓垪 1 -> 5 -> 7 -> 1 -> 5 -> 7 -> 1 
-> ... 杩欐牱鐨勮溅绔欒矾绾胯椹躲€?


 鐜板湪浠?source 杞︾珯鍑哄彂锛堝垵濮嬫椂涓嶅湪鍏氦杞︿笂锛夛紝瑕佸墠寰€ target 杞︾珯銆?鏈熼棿浠呭彲涔樺潗鍏氦杞︺€?

 姹傚嚭 鏈€灏戜箻鍧愮殑鍏氦杞︽暟閲?銆傚鏋滀笉鍙兘鍒拌揪缁堢偣杞︾珯锛岃繑鍥?-1 銆?



 绀轰緥 1锛?


杈撳叆锛歳outes = [[1,2,7],[3,6,7]], source = 1, target = 6
杈撳嚭锛?
瑙ｉ噴锛氭渶浼樼瓥鐣ユ槸鍏堜箻鍧愮涓€杈嗗叕浜よ溅鍒拌揪杞︾珯 7 , 鐒跺悗鎹箻绗簩杈嗗叕浜よ溅鍒拌溅绔?6 銆?


 绀轰緥 2锛?


杈撳叆锛歳outes = [[7,12],[4,5,15],[6],[15,19],[9,12,13]], source = 15, target = 12
杈撳嚭锛?1




 鎻愮ず锛?


 1 <= routes.length <= 500. 
 1 <= routes[i].length <= 105 
 routes[i] 涓殑鎵€鏈夊€?浜掍笉鐩稿悓 
 sum(routes[i].length) <= 105 
 0 <= routes[i][j] < 106 
 0 <= source, target < 106 

 Related Topics 骞垮害浼樺厛鎼滅储 鏁扮粍 鍝堝笇琛?
 馃憤 146 馃憥 0

[棰樼洰閾炬帴]

leetcode棰樼洰閾炬帴

[github鍦板潃]

浠ｇ爜閾炬帴

[鎬濊矾浠嬬粛]

鎬濊矾涓€锛欱FS

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• 鑰冭檻棰樿В鐨勬椂鍊欐湁濡備笅闂锛?/p>

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public int numBusesToDestination(int[][] routes, int source, int target) {

            //纭珛鎵€鏈夌嚎璺殑鍖呭惈鍏崇郴
            Map<Integer, Set<Integer>> map = new HashMap<>();
            for (int i = 0; i < routes.length; i++) {
                Set<Integer> set = new HashSet<>();
                for (int j = 0; j < routes[i].length; j++) {
                    set.add(routes[i][j]);
                }
                map.put(i, set);
            }

            //瀛樺偍绾胯矾绱㈠紩
            Deque<Integer> deque = new LinkedList<>();
            //璁板綍鍒板綋鍓嶇珯鐐圭殑绾胯矾鏁伴噺
            Map<Integer, Integer> res = new HashMap<>();
            //纭珛鍒濆绔欏彴
            for (Integer i : map.keySet()) {
                if (map.get(i).contains(source)) {
                    deque.add(i);
                    res.put(i, 1);
                }
            }
            //corner case
            if (deque.isEmpty()){
                return -1;
            }
            if (target==source){
                return 0;
            }
            while (!deque.isEmpty()) {
                int temp = deque.poll();
                int step = res.get(temp);
                for (int i : map.get(temp)) {
                    if (i == target) {
                        return step;
                    }
                    for (int line : map.keySet()) {
                        //鍖呭惈褰撳墠鑺傜偣鐨勭嚎璺叏閮ㄥ姞鍏ュ埌deque涓户缁箍搴︿紭鍏堥亶鍘?                        if (res.containsKey(line)) {
                            continue;
                        }
                        if (map.get(line).contains(i)) {
                            deque.add(line);
                            res.put(line, step + 1);
                        }
                    }

                }
            }
            return -1;

        }

鏃堕棿澶嶆潅搴($$\\sum_{0}^{n}routes+n^2$$)

n涓虹嚎璺暟锛屾眰鍜屽叕寮忎负姣忔潯绾胯矾涓婄珯鍙扮殑鏁伴噺鍜?/strong>