Slim Span UVA

Given an undirected weighted graph G, youshould find one of spanning trees specified as follows.The graph G is an ordered pair (V, E), whereV is a set of vertices {v1, v2, . . . , vn} and E is aset of undirected edges {e1, e2, . . . , em}. Eachedge e ∈ E has its weight w(e).A spanning tree T is a tree (a connected subgraphwithout cycles) which connects all the nvertices with n−1 edges. The slimness of a spanningtree T is defined as the difference betweenthe largest weight and the smallest weight among the n − 1 edges of T.For example, a graph G in Figure 5(a) has four vertices {v1, v2, v3, v4} and five undirected edges{e1, e2, e3, e4, e5}. The weights of the edges are w(e1) = 3, w(e2) = 5, w(e3) = 6, w(e4) = 6, w(e5) = 7as shown in Figure 5(b).Figure 6: Examples of the spanning trees of GThere are several spanning trees for G. Four of them are depicted in Figure 6(a)(d). The spanningtree Ta in Figure 6(a) has three edges whose weights are 3, 6 and 7. The largest weight is 7 and thesmallest weight is 3 so that the slimness of the tree Ta is 4. The slimnesses of spanning trees Tb, Tcand Td shown in Figure 6(b), (c) and (d) are 3, 2 and 1, respectively. You can easily see the slimnessof any other spanning tree is greater than or equal to 1, thus the spanning tree Td in Figure 6(d) is oneof the slimmest spanning trees whose slimness is 1.Your job is to write a program that computes the smallest slimness.InputThe input consists of multiple datasets, followed by a line containing two zeros separated by a space.Each dataset has the following format.n ma1 b1 w1...am bm wmEvery input item in a dataset is a non-negative integer. Items in a line are separated by a space.n is the number of the vertices and m the number of the edges. You can assume 2 ≤ n ≤ 100 and0 ≤ m ≤ n(n − 1)/2. ak and bk (k = 1, . . . , m) are positive integers less than or equal to n, whichrepresent the two vertices vakand vbkconnected by the k-th edge ek. wk is a positive integer less thanor equal to 10000, which indicates the weight of ek. You can assume that the graph G = (V, E) issimple, that is, there are no self-loops (that connect the same vertex) nor parallel edges (that are twoor more edges whose both ends are the same two vertices).OutputFor each dataset, if the graph has spanning trees, the smallest slimness among them should be printed.Otherwise, ‘-1’ should be printed. An output should not contain extra characters.Sample Input4 51 2 31 3 51 4 62 4 63 4 74 61 2 101 3 1001 4 902 3 202 4 803 4 402 11 2 13 03 11 2 13 31 2 22 3 51 3 65 101 2 1101 3 1201 4 1301 5 1202 3 1102 4 1202 5 1303 4 1203 5 1104 5 1205 101 2 93841 3 8871 4 27781 5 69162 3 77942 4 83362 5 53873 4 4933 5 66504 5 14225 81 2 12 3 1003 4 1004 5 1001 5 502 5 503 5 504 1 1500 0Sample Output1200-1-110168650

#include<stdio.h>#include<string.h>#include<iostream>#include<algorithm>using namespace std;#define MAX 2000000000int b[10000][10000],c[10001];struct STR{    int x,y,p;} a[10001];int find(int m){    if(c[m]==m)        return m;    else        return find(c[m]);}void merge(int x,int y){    int fx,fy;    fx=find(x);    fy=find(y);    if(fx>fy)    {        c[fx]=fy;    }    else        c[fy]=fx;}bool comp(STR q,STR w){    return q.p<w.p;}int main(){    int n,z,m,i,j,k,sum,min;    while(scanf("%d%d",&n,&m)&&(m!=0||n!=0))    {        memset(b,-1,sizeof(b));        for(i=0; i<m; i++)            scanf("%d%d%d",&a[i].x,&a[i].y,&a[i].p);        sort(a,a+m,comp);        for(i=0; i<m-n+2; i++)        {            k=0;memset(c,0,sizeof(c));           for(z=0;z<n;z++){c[z]=z;}            for(j=i; j<m; j++)            {                if(find(a[j].x)!=find(a[j].y))                {                    merge(a[j].x,a[j].y);                    b[i][k]=a[j].p;                    k++;                }            }        }        min=MAX;        for(i=0; i<m-n+2; i++)        {            sum=b[i][n-2]-b[i][0];            if(sum>=0&&sum<min)                min=sum;        }        if(min==MAX)            printf("-1\n");        else        printf("%d\n",min);    }    return 0;}