Hdu1068 girls and boys [maximum independent set]

Girls and boys Time Limit: 20000/10000 MS (Java/others) memory limit: 65536/32768 K (Java/Others) Total submission (s): 7710 accepted submission (s): 3535

Problem descriptionthe second year of the university somebody started a study on the romantic relations between the students. the relation "romantically involved" is defined between one girl and one boy. for the study reasons it is necessary to find out the maximum set satisfying the condition: there are no two students in the set who have been "romantically involved ". the result of the program is the number of students in such a set.

The input contains several data sets in text format. Each data set represents one set of subjects of the study, with the following description:

The number of students
The description of each student, in the following format
Student_identifier :( number_of_romantic_relations) student_identifier1 student_identifier2 student_identifier3...
Or
Student_identifier :( 0)

The student_identifier is an integer number between 0 and n-1, for N subjects.
For each given data set, the program shocould write to standard output a line containing the result.
 
Sample Input

70: (3) 4 5 61: (2) 4 62: (0)3: (0)4: (2) 0 15: (1) 06: (2) 0 130: (2) 1 21: (1) 02: (1) 0

 
Sample output

52

 
Sourcesoutheastern Europe 2000 question: there are n people, some people know others, select a set, so that everyone in the set does not know each other, and find the maximum number of people in the set. Question: this is to find the largest independent set, but this is not two sets, but a set, so after finding the maximum match,/2 is required, and then substitute the formula: maximum Independent Set = N-maximum match.

#include <stdio.h>#include <string.h>#define maxn 1010int n, B[maxn];bool vis[maxn];int head[maxn], id;struct Node {int v, next;} E[maxn * maxn];void addEdge(int u, int v) {E[id].v = v; E[id].next = head[u];head[u] = id++;}void getMap() {int i, u, k, v; id = 0;memset(head, -1, sizeof(int) * n);memset(B, -1, sizeof(int) * n);for(u = 0; u < n; ++u) {scanf("%*d: (%d)", &k);while(k--) {scanf("%d", &v);addEdge(u, v);}}}int findPath(int x) {int i, v;for(i = head[x]; i != -1; i = E[i].next) {if(!vis[v = E[i].v]) {vis[v] = 1;if(B[v] == -1 || findPath(B[v])) {B[v] = x; return 1;}}}return 0;}int MaxMatch() {int ans = 0, i;for(i = 0; i < n; ++i) {memset(vis, 0, sizeof(bool) * n);ans += findPath(i);}return ans;}void solve() {printf("%d\n", n - (MaxMatch() >> 1));}int main() {//freopen("stdin.txt", "r", stdin);while(scanf("%d", &n) == 1) {getMap();solve();}return 0;}

Hdu1068 girls and boys [maximum independent set]