hdu_2236

// hdu2236
// Graph Match  binary search + enumeration + bipartite
// Dec.26 2014

#include <cstdio>
#include <cstring>
#include <algorithm>

#define MaxN 111
#define ACCEPT

int G[MaxN][MaxN], T, n, max_edge, min_edge, l, r, mid, enum_edge, gx[MaxN], gy[MaxN];
bool vis[MaxN], is_match;

bool dfs(int u)
{
    for(int i = 1; i <= n; ++i){
        if(G[u][i] >= enum_edge && G[u][i] <= enum_edge + mid && vis[i] == false){
            vis[i] = true;
            if(gy[i] == -1 || dfs(gy[i]) == true){
                gy[i] = u;
                gx[u] = i;
                return true;
            }
        }
    }
    return false;
}

bool hungry()
{
    memset(gx, -1, sizeof(gx));
    memset(gy, -1, sizeof(gy));
    for(int i = 1; i <= n; ++i){
        memset(vis, false, sizeof(vis));
        if(dfs(i) == false)
            return false;
    }
}

int main(int argc, char const *argv[])
{
    #ifndef ACCEPT
        freopen("in.txt","r",stdin);
    #endif
    scanf("%d", &T);
    while(T--){
        // input , get the max num and min num
        max_edge = -1;
        min_edge = 101;
        scanf("%d", &n);
        for(int i = 1; i <= n; ++i){
            for(int j = 1; j <= n; ++j){
                scanf("%d", &G[i][j]);
                max_edge = std::max(G[i][j], max_edge);
                min_edge = std::min(G[i][j], min_edge);
            }
        }
        // 
        l = 0;
        r = max_edge - min_edge;
        while(true){
            mid  = (l + r) >> 1;
            is_match = false;
            for(enum_edge = min_edge; enum_edge + mid <= max_edge; ++enum_edge){
                if(hungry() == true){
                    is_match = true;
                    break;
                }
            }
            if(is_match == true)
                r = mid;
            if(l == mid)
                break;
            if(is_match == false)
                l = mid;
        }
        printf("%d
", r);
    }
    return 0;
}