{"id":1212,"date":"2010-04-20T18:22:17","date_gmt":"2010-04-20T10:22:17","guid":{"rendered":"http:\/\/www.slyar.com\/blog\/?p=1212"},"modified":"2022-07-03T15:46:58","modified_gmt":"2022-07-03T22:46:58","slug":"poj-3268-cpp","status":"publish","type":"post","link":"http:\/\/www.slyar.com\/blog\/poj-3268-cpp.html","title":{"rendered":"POJ 3268 Silver Cow Party C++\u7248"},"content":{"rendered":"

\u6587\u7ae0\u4f5c\u8005\uff1a\u59dc\u5357(Slyar) <\/span>\u6587\u7ae0\u6765\u6e90\uff1aSlyar Home (www.slyar.com<\/a>) \u8f6c\u8f7d\u8bf7\u6ce8\u660e\uff0c\u8c22\u8c22\u5408\u4f5c\u3002<\/p>\n

Dijkstra(\u5355\u6e90\u6700\u77ed\u8def\u5f84)\u7b97\u6cd5\u7684\u5e94\u7528<\/p>\n

<\/p>\n

Description<\/span><\/p>\n

One cow from each of N farms (1 \u2264 N \u2264 1000) conveniently numbered 1..N is going to attend the big cow party to be held at farm #X (1 \u2264 X \u2264 N). A total of M (1 \u2264 M \u2264 100,000) unidirectional (one-way roads connects pairs of farms; road i requires Ti (1 \u2264 Ti \u2264 100) units of time to traverse.<\/p>\n

Each cow must walk to the party and, when the party is over, return to her farm. Each cow is lazy and thus picks an optimal route with the shortest time. A cow's return route might be different from her original route to the party since roads are one-way.<\/p>\n

Of all the cows, what is the longest amount of time a cow must spend walking to the party and back?<\/p>\n

Input<\/span><\/p>\n

Line 1: Three space-separated integers, respectively: N, M, and X
\nLines 2..M+1: Line i+1 describes road i with three space-separated integers: Ai, Bi, and Ti. The described road runs from farm Ai to farm Bi, requiring Ti time units to traverse.<\/p>\n

Output<\/span><\/p>\n

Line 1: One integer: the maximum of time any one cow must walk.<\/p>\n

Sample Input<\/span><\/p>\n

4 8 2
\n1 2 4
\n1 3 2
\n1 4 7
\n2 1 1
\n2 3 5
\n3 1 2
\n3 4 4
\n4 2 3<\/p>\n

Sample Output<\/span><\/p>\n

10<\/p>\n

Slyar:\u9898\u76ee\u5927\u610f\u662f\u7ed9\u51fa\u4e00\u4e2a\u6709\u5411\u56fe\u7684\u5e26\u6743\u90bb\u63a5\u77e9\u9635\uff0c\u7136\u540e\u7ed9\u5b9a\u76ee\u6807\u8282\u70b9X\uff0c\u6c42\u51fa\u5176\u4f59\u7ed3\u70b9\u51fa\u53d1\u5230\u7ed3\u70b9X\u518d\u4eceX\u56de\u5230\u51fa\u53d1\u7ed3\u70b9\u7684\u6700\u77ed\u8def\u5f84\u548c\u4e2d\u6700\u5927\u7684\u90a3\u4e2a...=_=\u662f\u4e0d\u662f\u5f88\u6655\uff1f\u6655\u7684\u8bdd\u53bb\u770b\u82f1\u6587...<\/span><\/p>\n

\u6069\uff0c\u6709\u5411\u56fe\uff0c\u5230X\u518d\u4eceX\u56de\u6765\uff0c\u4eceX\u56de\u6765\u7b80\u5355\uff0c\u4e00\u4e2aDijkstra\u5c31\u641e\u5b9a\uff0c\u5230X\u5c31\u6bd4\u8f83\u9ebb\u70e6\u4e86\uff0c\u4e00\u5f00\u59cb\u7528Flyod\u505a\uff0c\u7ed3\u679c\u8d85\u65f6...=_=\u540e\u6765\u53d1\u73b0\u53ea\u8981\u628a\u77e9\u9635\u8f6c\u7f6e\u4e00\u4e0b\u5c31\u597d\u4e86\uff0c\u8f6c\u7f6e\u4ee5\u540e\u5c31\u53c8\u76f8\u5f53\u4e8e\u4eceX\u51fa\u53d1\u4e86\uff0c\u518d\u6765\u4e00\u6b21Dijkstra\u641e\u5b9a...\u5f88\u597d\u7406\u89e3\u7684...<\/span><\/p>\n

\r\n#include \r\n\r\nusing namespace std;\r\n\r\nconst int N = 1010;\r\nconst int MAX = 1000001;\r\nint n, m;\r\nint map1[N][N];\r\nint map2[N][N];\r\nint dist1[N];\r\nint dist2[N];\r\n\r\n\/\/ dist[]\u8bb0\u5f55\u8282\u70b9x\u5230\u5176\u4f59\u5404\u70b9\u7684\u6700\u77ed\u8def\u5f84\u957f\u5ea6\r\nvoid dijkstra(int map[][N], int dist[], int x)\r\n{\r\n\tint u, min;\r\n\t\/\/ \u8bb0\u5f55\u8282\u70b9\u662f\u5426\u6c42\u89e3\u5b8c\u6bd5\r\n\tint visited[N] = {0};\r\n\t\/\/ \u8282\u70b9x\u5230\u81ea\u5df1\u7684\u8ddd\u79bb\u4e3a0\r\n\tdist[x] = 0;\r\n\t\/\/ \u6c42\u89e3\u5176\u4f59n-1\u4e2a\u8282\u70b9\u5230x\u7684\u6700\u77ed\u8def\u5f84\r\n\tfor (int i = 1; i <= n; i++)\r\n\t{\r\n\t\t\/\/ \u9009\u62e9\u4e0e\u5f53\u524d\u8282\u70b9\u76f8\u90bb\u4e14\u672a\u8bbf\u95ee\u7684\u8282\u70b9\u4e2d\u8ddd\u79bb\u6700\u77ed\u7684\u8282\u70b9u\r\n\t\tfor (int j = 1; j <= n; j++)\r\n\t\t{\r\n\t\t\tif (!visited[j] && dist[j] < min)\r\n\t\t\t{\r\n\t\t\t\tmin = dist[j];\r\n\t\t\t\tu = j;\r\n\t\t\t}\r\n\t\t}\r\n\t\t\/\/ \u6807\u8bb0u\u5df2\u6c42\u89e3\r\n\t\tvisited[u] = 1;\r\n\t\t\/\/ \u6839\u636eu\u6765\u66f4\u65b0\u5176\u4f59\u8282\u70b9\r\n\t\tfor (int j = 1; j <= n; j++)\r\n\t\t{\r\n\t\t\tif (!visited[j] && dist[j] > dist[u] + map[u][j])\r\n\t\t\t{\r\n\t\t\t\tdist[j] = dist[u] + map[u][j];\r\n\t\t\t}\r\n\t\t}\r\n\t}\r\n}\r\n\r\nint main()\r\n{\r\n\tint ai, bi, ti, x;\r\n\tint ans = 0;\r\n\tcin >> n >> m >> x;\r\n\t\/\/\u521d\u59cb\u5316\r\n\tfor (int i = 1; i <= n; i++)\r\n\t{\r\n\t\tfor (int j = 1; j <= n; j++)\r\n\t\t{\r\n\t\t\tmap1[i][j] = MAX;\r\n\t\t\tmap2[i][j] = MAX;\r\n\t\t}\r\n\t\tdist1[i] = MAX;\r\n\t\tdist2[i] = MAX;\r\n\t}\r\n\t\/\/\u8bfb\u5165\u77e9\u9635\r\n\tfor (int i = 1; i <= m; i++)\r\n\t{\r\n\t\tcin >> ai >> bi >> ti;\r\n\t\tmap1[ai][bi] = ti;\r\n\t\tmap2[bi][ai] = ti;\r\n\t}\r\n\r\n\tdijkstra(map1, dist1, x);\r\n\tdijkstra(map2, dist2, x);\r\n\r\n\tfor (int i = 1; i <= n; i++)\r\n\t{\r\n\t\tif (ans < dist1[i] + dist2[i])\r\n\t\t{\r\n\t\t\tans = dist1[i] + dist2[i];\r\n\t\t}\r\n\t}\r\n\r\n\tcout << ans << endl;\r\n\treturn 0;\r\n}\r\n<\/pre>\n
\u8f6c\u8f7d\u8bf7\u6ce8\u660e\uff1aSlyar Home<\/a> » POJ 3268 Silver Cow Party C++\u7248<\/a><\/p>","protected":false},"excerpt":{"rendered":"
\u6587\u7ae0\u4f5c\u8005\uff1a\u59dc\u5357(Slyar) \u6587\u7ae0\u6765\u6e90\uff1aSlyar Home (www.slyar.com) \u8f6c\u8f7d\u8bf7\u6ce8\u660e\uff0c\u8c22\u8c22\u5408\u4f5c\u3002 Dijkstra(\u5355\u6e90\u6700\u77ed\u8def\u5f84)\u7b97\u6cd5\u7684\u5e94\u7528 \u8f6c\u8f7d\u8bf7\u6ce8\u660e\uff1aSlyar Home » POJ 3268 Silver Cow […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1103],"tags":[1006],"class_list":["post-1212","post","type-post","status-publish","format-standard","hentry","category-acm-oj-solution","tag-poj"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t