Problem:
Score : 500 points

Problem Statement

In Takahashi Kingdom, which once existed, there are N cities, and some pairs of cities are connected bidirectionally by roads.
The following are known about the road network:

People traveled between cities only through roads. It was possible to reach any city from any other city, via intermediate cities if necessary.

Different roads may have had different lengths, but all the lengths were positive integers.

Snuke the archeologist found a table with N rows and N columns, A, in the ruin of Takahashi Kingdom.
He thought that it represented the shortest distances between the cities along the roads in the kingdom.

Determine whether there exists a road network such that for each u and v, the integer A_{u, v} at the u-th row and v-th column of A is equal to the length of the shortest path from City u to City v.
If such a network exist, find the shortest possible total length of the roads.

Constraints

1 \leq N \leq 300

If i ≠ j, 1 \leq A_{i, j} = A_{j, i} \leq 10^9.

A_{i, i} = 0

Inputs

Input is given from Standard Input in the following format:

N
A_{1, 1} A_{1, 2} ... A_{1, N}
A_{2, 1} A_{2, 2} ... A_{2, N}
...
A_{N, 1} A_{N, 2} ... A_{N, N}

Outputs

If there exists no network that satisfies the condition, print -1.
If it exists, print the shortest possible total length of the roads.

Sample Input 1

3
0 1 3
1 0 2
3 2 0

Sample Output 1

3

The network below satisfies the condition:

City 1 and City 2 is connected by a road of length 1.

City 2 and City 3 is connected by a road of length 2.

City 3 and City 1 is not connected by a road.

Sample Input 2

3
0 1 3
1 0 1
3 1 0

Sample Output 2

-1

As there is a path of length 1 from City 1 to City 2 and City 2 to City 3, there is a path of length 2 from City 1 to City 3.
However, according to the table, the shortest distance between City 1 and City 3 must be 3.

Thus, we conclude that there exists no network that satisfies the condition.

Sample Input 3

5
0 21 18 11 28
21 0 13 10 26
18 13 0 23 13
11 10 23 0 17
28 26 13 17 0

Sample Output 3

82

Sample Input 4

3
0 1000000000 1000000000
1000000000 0 1000000000
1000000000 1000000000 0

Sample Output 4

3000000000

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.io.*;
import java.util.*;

class Main{

    void solve(){        
        int N = ni();

        long[][] dist = new long[N + 1][N + 1];
        long[][] dp = new long[N+1][N+1];
        boolean[][] not = new boolean[N + 1][N + 1];
        fill(dp, LINF / 2);
        for(int i = 1; i <= N; i++){
            for(int j = 1; j <= N; j++){
                dist[i][j] = dist[j][i] = dp[i][j] = dp[j][i] = ni();
            }
        }
        
        for(int k = 1; k <= N; k++){
            for(int i = 1; i <= N; i++){
                for(int j = 1; j <= N; j++){
                    if(k != i && i != j && k != j && dp[i][j] >= dp[i][k] + dp[k][j]){
                        not[min(i, j)][max(i, j)] = true;
                    }
                    dp[i][j] = min(dp[i][j], dp[i][k] + dp[k][j]);
                }
            }
        }

        long ans = 0;
        for(int i = 1; i < N; i++){ 
            for(int j = i + 1; j <= N; j++){ 
                if(dist[i][j] != dp[i][j]){
                    System.out.println(-1);
                    return;
                }
                if(!not[i][j]){
                    ans += dp[i][j];
                }
            }
        }

        System.out.println(ans);

    }

    public static void main(String[] args){
        new Main().solve();
    }

    private FastScanner scan = new FastScanner();
    private final int MOD = 1_000_000_007;
    private final int INF = 2147483647;
    private final long LINF = 9223372036854775807L;
    private long[] fac;
    private long[] finv;
    private long[] inv;

    // Scanner
    int ni(){ return scan.nextInt();}
    int[] ni(int n){int[] a = new int[n]; for(int i = 0; i < n; i++){a[i] = ni();} return a;}
    int[][] ni(int y, int x){int[][] a = new int[y][x];
        for(int i = 0; i < y; i++){for(int j = 0; j < x; j++){a[i][j] = ni();}} return a;}
    long nl(){return scan.nextLong();}
    long[] nl(int n){long[] a = new long[n]; for(int i = 0; i < n; i++){a[i] = nl();} return a;}
    long[][] nl(int y, int x){long[][] a = new long[y][x];
        for(int i = 0; i < y; i++){for(int j = 0; j < x; j++){a[i][j] = nl();}} return a;}
    String ns(){return scan.next();}
    String[] ns(int n){String[] a = new String[n]; for(int i = 0; i < n; i++){a[i] = ns();} return a;}
    String[][] ns(int y, int x){String[][] a = new String[y][x];
        for(int i = 0; i < y; i++){for(int j = 0; j < x; j++){a[i][j] = ns();}} return a;}

    // Mathmatics
    int max(int a, int b){return Math.max(a, b);}
    long max(long a, long b){return Math.max(a, b);}
    double max(double a, double b){return Math.max(a, b);}
    int max(int[] a){int max = a[0]; for(int value:a){max = max(max,value);} return max;}
    long max(long[] a){long max = a[0]; for(long value:a){max = max(max,value);} return max;}
    double max(double[] a){double max = a[0]; for(double value:a){max = max(max,value);} return max;}
    int min(int a, int b){return Math.min(a, b);}
    long min(long a, long b){return Math.min(a, b);}
    double min(double a, double b){return Math.min(a, b);}
    int min(int[] a){int min = a[0]; for(int value:a){min = min(min,value);} return min;}
    long min(long[] a){long min = a[0]; for(long value:a){min = min(min,value);} return min;}
    double min(double[] a){double min = a[0]; for(double value:a){min = min(min,value);} return min;}
    long sum(int[] a){long sum = 0; for(int value:a){sum += value;} return sum;}
    long sum(long[] a){long sum = 0; for(long value:a){sum += value;} return sum;}
    double sum(double[] a){double sum = 0; for(double value:a){sum += value;} return sum;}
    int gcd(int a, int b){return b == 0 ? a : gcd(b, a % b);}
    long gcd(long a, long b){return b == 0 ? a : gcd(b, a % b);}
    int lcm(int a, int b){return a / gcd(a, b) * b;}
    long lcm(long a, long b){return a / gcd(a, b) * b;}
    long fact(int n){ if(n == 0){ return 1; } long a = n; for(long i = n - 1; i >= 2; i--){ a = a % MOD * i; } return a; }
    long fact(long n){ if(n == 0){ return 1; } long a = n; for(long i = n - 1; i >= 2; i--){ a = a % MOD * i; } return a; }
    // nPr(int)
    long npr(int n, int r){
        long a = 1;
        for(int i = n; i > n - r; i--){
            a *= i;
        }
        return a;
    }
    // nPr(long)
    long npr(long n, long r){
        long a = 1;
        for(long i = n; i > n - r; i--){
            a *= i;
        }
        return a;
    }
    // 素数判定(int)
    boolean checkPrime(int n){
        for(int i = 2; i * i <= n; i++){
            if(n % i == 0){
                return false;
            }
        }
        return true;
    }
    // 素数判定(long)
    boolean checkPrime(long n){
        for(long i = 2; i * i <= n; i++){
            if(n % i == 0){
                return false;
            }
        }
        return true;
    }
    // mod pにおける累乗 a^n
    long modpow(long a, long n, long p){
        long res = 1;
        while(n > 0){
            if((n & 1) == 1){
                res = res * a % p;
            }
            a = a * a % p;
            n = n >> 1;
        }
        return res;
    }
    // mod pにおけるaの逆元a^-1
    long modinv(long a, long p){
        return modpow(a, p - 2, p);
    }
    // fac,finv,invの初期化
    void comInit(int max){
        fac = new long[max];
        finv = new long[max];
        inv = new long[max];
        fac[0] = fac[1] = 1;
        finv[0] = finv[1] = 1;
        inv[1] = 1;
        for(int i = 2; i < max; i++){
            fac[i] = fac[i - 1] * i % MOD;
            inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
            finv[i] = finv[i - 1] * inv[i] % MOD;
        }
    }
    // 二項係数nCr
    long com(int n, int r){
        if(n < r || (n < 0 || r < 0)){
            return 0;
        }
        return fac[n] * (finv[r] * finv[n - r] % MOD) % MOD;
    }
    // 二項係数nCr（nが10^9など巨大なとき用）
    long ncr(long n, long k){
        long a = 1;
        long b = 1;
        for(int i = 1; i <= k; i++){
            a = a * (n + 1 - i) % MOD;
            b = b * i % MOD;
        }
        
        return modinv(b, MOD) * a % MOD;
    }


    // Array
    void sort(int[] a){ Arrays.sort(a);}
    void sort(long[] a){ Arrays.sort(a);}
    void sort(double[] a){ Arrays.sort(a);}
    void sort(String[] a){ Arrays.sort(a);}
    int[] reverse(int[] a){
        int[] reversed = new int[a.length];
        for(int i = 0; i < a.length; i++){
            reversed[a.length - i - 1] = a[i];
        }
        return reversed;
    }
    long[] reverse(long[] a){
        long[] reversed = new long[a.length];
        for(int i = 0; i < a.length; i++){
            reversed[a.length - i - 1] = a[i];
        }
        return reversed;
    }
    double[] reverse(double[] a){
        double[] reversed = new double[a.length];
        for(int i = 0; i < a.length; i++){
            reversed[a.length - i - 1] = a[i];
        }
        return reversed;
    }
    char[] reverse(char[] a){
        char[] reversed = new char[a.length];
        for(int i = 0; i < a.length; i++){
            reversed[a.length - i - 1] = a[i];
        }
        return reversed;
    }
    String[] reverse(String[] a){
        String[] reversed = new String[a.length];
        for(int i = 0; i < a.length; i++){
            reversed[a.length - i - 1] = a[i];
        }
        return reversed;
    }
    boolean[] reverse(boolean[] a){
        boolean[] reversed = new boolean[a.length];
        for(int i = 0; i < a.length; i++){
            reversed[a.length - i - 1] = a[i];
        }
        return reversed;
    }
    void fill(int[] array, int x) { Arrays.fill(array, x); }
    void fill(long[] array, long x) { Arrays.fill(array, x); }
    void fill(double[] array, double x) { Arrays.fill(array, x); }
    void fill(boolean[] array, boolean x) { Arrays.fill(array, x); }
    void fill(int[][] array, int x) { for(int a[] : array) { fill(a, x); } }
    void fill(long[][] array, long x) { for(long a[] : array) { fill(a, x); } }
    void fill(double[][] array, double x) { for(double a[] : array) { fill(a, x); } }
    void fill(boolean[][] array, boolean x) { for(boolean a[] : array) { fill(a, x); } }
    void fill(int[][][] array, int x) { for(int[][] ary : array) { for(int[] a : ary){ fill(a, x); } } }
    void fill(long[][][] array, long x) { for(long[][] ary : array) { for(long[] a : ary){ fill(a, x); } } }

    // Algorithm
    // 深さ優先探索
    /*
        HashMap<Integer, List<Integer>> graph = new HashMap<>();
        List<Integer> list;
    */
    int minCost = INF;
    void dfs(HashMap<Integer, List<Integer>> graph, int v, boolean[] seen, int[] cost, PriorityQueue<Integer> queue){
        seen[v] = true;
        queue.add(cost[v]);
        if(!graph.containsKey(v) || graph.get(v).size() == 0) return;
        List<Integer> todo = graph.get(v);
        for(int next : todo){
            if(seen[next]) continue;
            dfs(graph, next, seen, cost, queue);
        }
    }
    // 幅優先探索
    /*
        HashMap<Integer, List<Integer>> graph = new HashMap<>();
        List<Integer> list;
    */
    void bfs(HashMap<Integer, List<Integer>> graph, int v, int[] dist){
        Queue<Integer> que = new ArrayDeque<>();
        que.add(v);

        while(que.size() > 0){
            v = que.poll();
            if(!graph.containsKey(v)) continue;
            for(int next : graph.get(v)){
                if(dist[next] != -1) continue;
                dist[next] = dist[v] + 1;
                que.add(next);
            }
        }
    }
    // ダイクストラ法
    Node[] dijkstra(HashMap<Integer, List<Integer>> graph, int size, int v, boolean[] flag, int[][] cost){
        Queue<Node> queue = new PriorityQueue<>(new MyComparator());
        Node[] nodes = new Node[size];
        for(int i = 1; i < size; i++){
            nodes[i] = new Node(i, INF, -1);            // id, dist, pastを指定して初期化
        }
        /* for(int key : graph.keySet()){
            nodes[key] = new Node(key, INF, -1);    // id, dist, pastを指定して初期化
        } */
       
        nodes[v].dist = 0;  // 始点のコストを0に
        try{
            queue.add(nodes[v].clone());
        } catch(CloneNotSupportedException e){
            e.printStackTrace();
        }

        while(queue.size() > 0){
            Node now = queue.poll();        // 未確定の中で最もコストの低いノードを取り出す
            flag[now.id] = true;                // 確定
            if(!graph.containsKey(now.id)) continue;
            for(int next : graph.get(now.id)){      // 辺で繋がっているノードを順にチェック
                if(flag[next] || nodes[next].dist < nodes[now.id].dist + cost[now.id][next]) continue;
                nodes[next].dist = nodes[now.id].dist + cost[now.id][next];     // distを更新
                nodes[next].past = now.id;                                                    // pastを現在のノードに
                try{
                    queue.add(nodes[next].clone());
                } catch (CloneNotSupportedException e){
                    e.printStackTrace();
                }
            }
        }

        return nodes;
    }
    
    // ソート済みint型配列でkey以上の値の最小indexを返す
    int lowerBound(int[] a, int key){
        int ng = -1;
        int ok = a.length;
        while(Math.abs(ok - ng) > 1){
            int mid = (ok + ng) / 2; 
            if(a[mid] >= key){
                ok = mid;
            } else {
                ng = mid;
            }
        }
        return ok;
    }
    // ソート済みlong型配列でkey以上の値の最小indexを返す
    int lowerBound(long[] a, long key){
        int ng = -1;
        int ok = a.length;
        while(Math.abs(ok - ng) > 1){
            int mid = (ok + ng) / 2; 
            if(a[mid] >= key){
                ok = mid;
            } else {
                ng = mid;
            }
        }
        return ok;
    }
    // 文字列sとtの最長共通部分列の長さを返す
    int lcs(String s , String t){
        int[][] dp = new int[s.length() + 1][t.length() + 1];

        for(int i = 0; i < s.length(); i++){
            for(int j = 0; j < t.length(); j++){
                if(s.charAt(i) == t.charAt(j)){
                    dp[i + 1][j + 1] = max(dp[i][j] + 1, dp[i + 1][j + 1]);
                }
                dp[i + 1][j + 1] = max(dp[i + 1][j + 1], dp[i + 1][j]);
                dp[i + 1][j + 1] = max(dp[i + 1][j + 1], dp[i][j + 1]);
            }
        }

        return dp[s.length()][t.length()];
    }

}
// ダイクストラ法におけるノード
class Node implements Cloneable{
    int id;             // ノード番号
    int dist;           // 最低必要コスト
    int past;           // 直前の頂点

    Node(int id, int dist, int past){
        this.id = id;
        this.dist = dist;
        this.past = past;
    }
    @Override
    protected Node clone() throws CloneNotSupportedException{
        Node node = (Node)super.clone();
        return node;
    }
}
// ダイクストラ法における重み比較のComparator
class MyComparator implements Comparator<Node>{
    @Override
    public int compare(Node n1, Node n2){
        int dist1 = n1.dist;
        int dist2 = n2.dist;
        if(dist1 < dist2){
            return -1;
        } else if(dist1 > dist2){
            return 1;
        } else {
            return 0;
        }
    }
}

// 順列を管理する
class Permutation {
    private int number;
    private int listSize;
    private int searched;
    private int nextIndex;
    private int[][] permList;

    Permutation(int num) {
        this.number = num;
        this.listSize  = this.fact(this.number);
        this.searched   = 0;
        this.nextIndex = 0;
        this.permList  = new int[this.listSize][this.number];

        this.create(0, new int[this.number], new boolean[this.number]);
    }

    int[] nextPerm() {
        return permList[this.nextIndex++];
    }

    boolean isNext() {
        if(this.nextIndex < this.listSize) {
            return true;
        } else {
            this.nextIndex = 0;
            return false;
        }
    }

    int fact(int n){
        return n == 0 ? 1 : n * fact(n-1);
    }

    void create(int num, int[] list, boolean[] flag) {
        if(num == this.number) {
            copyArray(list, permList[this.searched]);
            this.searched++;
        }
        for(int i = 0; i < this.number; i++){
            if(flag[i]) continue;
            list[num] = i;
            flag[i] = true;
            this.create(num+1, list, flag);
            flag[i] = false;

        }
    }

    void copyArray(int[] from, int[] to) {
        for(int i=0; i<from.length; i++) to[i] = from[i];
    }

    void printNum(int[] nums) {
        for(int n : nums) System.out.print(n);
        System.out.println();
    }
}

// 標準のScannerより高速に標準入力する
class FastScanner {
    private final InputStream in = System.in;
    private final byte[] buffer = new byte[1024];
    private int ptr = 0;
    private int buflen = 0;
    private boolean hasNextByte() {
        if (ptr < buflen) {
            return true;
        }else{
            ptr = 0;
            try {
                buflen = in.read(buffer);
            } catch (IOException e) {
                e.printStackTrace();
            }
            if (buflen <= 0) {
                return false;
            }
        }
        return true;
    }
    private int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1;}
    private static boolean isPrintableChar(int c) { return 33 <= c && c <= 126;}
    public boolean hasNext() { while(hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++; return hasNextByte();}
    public String next() {
        if (!hasNext()) throw new NoSuchElementException();
        StringBuilder sb = new StringBuilder();
        int b = readByte();
        while(isPrintableChar(b)) {
            sb.appendCodePoint(b);
            b = readByte();
        }
        return sb.toString();
    }
    public long nextLong() {
        if (!hasNext()) throw new NoSuchElementException();
        long n = 0;
        boolean minus = false;
        int b = readByte();
        if (b == '-') {
            minus = true;
            b = readByte();
        }
        if (b < '0' || '9' < b) {
            throw new NumberFormatException();
        }
        while(true){
            if ('0' <= b && b <= '9') {
                n *= 10;
                n += b - '0';
            }else if(b == -1 || !isPrintableChar(b)){
                return minus ? -n : n;
            }else{
                throw new NumberFormatException();
            }
            b = readByte();
        }
    }
    public int nextInt() {
        long nl = nextLong();
        if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE) throw new NumberFormatException();
        return (int) nl;
    }
    public double nextDouble() { return Double.parseDouble(next());}
}