bzoj 2756

传送门http://www.lydsy.com/JudgeOnline/problem.php?id=2756

基本思路：我们考虑可以变成的最终的状态，假设每一位置的数都是x， 由于对于相连的格子一起加1， 那么我们就可以对方格进行黑白染色（相邻格子的颜色严格不同），假设个数分别为c1， c2， 总和为s1， s2， 那么 c1 * x - s1 = c2 * x - s2, x = (s1 - s2) / (c1 - c2); 当n * m % 2 == 1 时 c1 != c2, 可以反解x; 否则x在某一个值以上的时候一定都可以满足，就可以二分了。

重点就是如何检验x是否可行，然后方法是对于黑格子向原点连x - a[i][j] 的边，然后白格子向汇点连x - a[i][j]的边， 然后相邻的格子连inf的边，跑满流就可以了。

warning: 首先我们需要两个inf 分别表示流量的最大值和二分最大值，不能一样，然后二分的最小边界必须是a[i][j] 中的最大值减1，因为要保证x > Max{a[i][j]}

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;

typedef long long qword;

const qword maxl = 50;
const qword maxn = maxl * maxl;
const qword dir[4][2] = {{1, 0}, {-1, 0}, {0, 1}, {0, -1}};
const qword inf = 0x3f3f3f3f;
const qword infll = (1ll << 60);

qword n, m, sum[2], c[2];
qword a[maxl][maxl], col[maxl][maxl];

struct edge {
    qword t, c;
    edge* next, *other;
}e[maxn * 10]; qword ne = 0; edge* head[maxn];

void addedge(qword f, qword t, qword c) {
    e[ne].t = t, e[ne].c = c, e[ne].next = head[f], head[f] = e + ne ++;
    e[ne].t = f, e[ne].c = 0, e[ne].next = head[t], head[t] = e + ne ++;
    e[ne - 1].other = e + ne - 2;
    e[ne - 2].other = e + ne - 1;
}

qword q[maxn], l, r; qword dis[maxn];
qword s, t;

bool bfs() {
    memset(dis, 0, sizeof(dis));
    dis[s] = 1;
    l = r = 0; q[r ++] = s;
    while(l ^ r) {
        qword x = q[l ++];
        for(edge* p = head[x]; p; p = p-> next) {
            if(!dis[p-> t] && p-> c) {
                q[r ++] = p-> t; dis[p-> t] = dis[x] + 1;
            }
        }
    }
    return (bool)dis[t];
}

/*qword dfs(qword x, qword flow) {
    if(x == t) return flow;
    if(!flow) return 0;
    qword ret = 0, maxflow;
    for(edge* p = head[x]; p && flow; p = p-> next) {
        if(p-> c && dis[p-> t] == dis[x] + 1 && (maxflow = dfs(p-> t, min(flow, p-> c)))) {
            p-> c -= maxflow, p-> other-> c += maxflow;
            ret += maxflow, flow -= maxflow;
        }
    }
    return ret;
}*/

edge* Next[maxn]; qword sta[maxn], top = 0;

qword dfs() {
    for(qword i = s; i <= t; ++ i) Next[i] = head[i];
    top = 0;
    sta[++ top] = s; 
    qword ret = 0;
    while(top) {
        qword x = sta[top];
        if(x == t) {
            qword minfl = infll + 1000;
            qword last;
            for(qword i = 1; i < top; ++ i) {
                if(Next[sta[i]]-> c < minfl) 
                    minfl = Next[sta[i]]-> c, last = i;
            }
            for(qword i = 1; i < top; ++ i) {
                edge* p = Next[sta[i]];
                p-> c -= minfl, p-> other-> c += minfl;
            }
            ret += minfl, top = last;
            continue;
        }
        edge* px;
        for(px = Next[x]; px; px = px-> next) {
            if(dis[px-> t] == dis[x] + 1 && px-> c) {
                sta[++ top] = px-> t; break;
            }
        }
        Next[x] = px;
        if(Next[x] == NULL) {
            top --;
            if(Next[sta[top]]) Next[sta[top]] = Next[sta[top]]-> next;
        }
    }
    return ret;
}

qword get(qword x, qword y) {
    return (x - 1) * m + y;
}

bool flow(qword x) {
    ne = 0;
    memset(head, 0, sizeof(head));
    qword tl = 0;
    for(qword i = 1; i <= n; ++ i) {
        for(qword j = 1; j <= m; ++ j) {
            qword tmp = x - a[i][j];
            if(col[i][j] == 0) addedge(0, get(i, j), tmp);
            else addedge(get(i, j), t, tmp);
            tl += tmp;
        }
    }
    for(qword i = 1; i <= n; ++ i) {
        for(qword j = 1; j <= m; ++ j) {
            if(col[i][j] == 0) {
                for(qword l = 0; l < 4; ++ l) {
                    qword x = i + dir[l][0];
                    qword y = j + dir[l][1];
                    if(x < 1 || x > n || y < 1 || y > m) continue;
                    addedge(get(i, j), get(x, y), infll);
                }
            }
        }
    }
    qword fl = 0;
    while(bfs()) fl += dfs();
    return (tl == fl * 2);
}

qword getans(qword x) {
    return ((n * m * x - sum[0] - sum[1]) >> 1);
}

void sov() {
    qword T; scanf("%lld", &T);
    qword Max = 0;
    while(T --) {
        Max = 0;
        scanf("%lld%lld", &n, &m);
        memset(sum, 0, sizeof(sum)); 
        memset(c, 0, sizeof(c));
        col[0][1] = 1;
        for(qword i = 1; i <= n; ++ i) {
            qword cl = !col[i - 1][1];
            for(qword j = 1; j <= m; ++ j) {
                scanf("%lld", &a[i][j]);
                col[i][j] = cl; cl = !cl;
                c[col[i][j]] ++, sum[col[i][j]] += a[i][j];
                Max = max(Max, a[i][j]);
            }
        }
        s = 0, t = n * m + 1;
        if(n * m % 2) {
            qword x = abs(sum[0] - sum[1]);
            if(x >= Max && flow(x)) printf("%lld
", getans(x));
            else printf("-1
");
        }
        else {
            qword ls = Max - 1, rs = inf * 1000;
            qword ans = -1;
            while(rs - ls > 1) { 
                qword mid = (ls + rs) >> 1;
                if(flow(mid)) rs = mid, ans = mid;
                else ls = mid;
            }
            if(ans == -1) printf("-1
");
            else printf("%lld
", getans(ans));
        }
    }
}

int main() {
    //freopen("test.in", "r", stdin);
    //freopen("test.out", "w", stdout);
    sov();
    return 0;
}