zoj 2158 prim

http://acm.zju.edu.cn/onlinejudge/showProblem.do?problemId=1158

#include <cstdio>#include <cstdlib>#include <cstring>#define INF 1000000#define MAXN 2000int N;char codes[MAXN][10];int d[MAXN][MAXN];int lowcost[MAXN];int prim(){int i, j, k;int dist;memset( d, 0, sizeof(d) );for( i = 0; i < N; i++ ){for( j = i+1; j < N; j++ ){dist = 0;for( k = 0; k < 7; k++ )                if(codes[j][k]!= codes[i][k])                dist++; d[i][j] = d[j][i] = dist;}}int sum = 0;lowcost[0] = -1;for( i = 1; i < N; i ++ )lowcost[i] = d[0][i];for( i = 1; i < N; i++ ){int min = INF;for( k = 0; k < N; k++ ){if( lowcost[k] != -1  &&  lowcost[k] < min ){j = k;min = lowcost[k];}}sum += min;lowcost[j] = -1;for( k = 0; k < N; k ++ ){if( d[j][k] < lowcost[k] )lowcost[k] = d[j][k];}}return sum;}int main(){int i;//freopen("1.txt","r",stdin);while( 1 ){scanf( "%d", &N );if( N==0 )            break;for( i = 0; i < N; i++ )scanf( "%s", codes[i] );printf( "The highest possible quality is 1/%d.\n", prim());}return 0;}