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  • hdu 1569 最大点权独立集

    参考网上大牛的方法做的,A了,但做法的可行性我还没有想明白。慢慢再想吧,先贴代码~

    /*
    * hdu1569/win.cpp
    * Created on: 2011-10-5
    * Author : ben
    */
    #include <cstdio>
    #include <cstdlib>
    #include <cstring>
    #include <cmath>
    #include <algorithm>
    #include <iostream>
    #include <queue>
    using namespace std;

    typedef int typec;
    const typec inf = 0x7fffffff;
    const int MAXE = 40000;
    const int MAXN = 3000;
    typedef struct {
    int x, y, nxt;
    typec c;
    } Edge;
    Edge bf[MAXE];
    int ne, head[MAXN], cur[MAXN], ps[MAXN], dep[MAXN];
    int map[MAXN][MAXN];
    typec sum;

    inline void addedge(int x, int y, typec c) {
    bf[ne].x = x;
    bf[ne].y = y;
    bf[ne].c = c;
    bf[ne].nxt = head[x];
    head[x] = ne++;
    bf[ne].x = y;
    bf[ne].y = x;
    bf[ne].c = 0;
    bf[ne].nxt = head[y];
    head[y] = ne++;
    }

    typec flow(int n, int s, int t) {
    typec tr, res = 0;
    int i, j, k, f, r, top;
    while (1) {
    memset(dep, -1, n * sizeof(int));
    for (f = dep[ps[0] = s] = 0, r = 1; f != r;) {
    for (i = ps[f++], j = head[i]; j; j = bf[j].nxt) {
    if (bf[j].c && -1 == dep[k = bf[j].y]) {
    dep[k] = dep[i] + 1;
    ps[r++] = k;
    if (k == t) {
    f = r;
    break;
    }
    }
    }
    }
    if (-1 == dep[t]) {
    break;
    }
    memcpy(cur, head, n * sizeof(int));
    for (i = s, top = 0;;) {
    if (i == t) {
    for (k = 0, tr = inf; k < top; ++k) {
    if (bf[ps[k]].c < tr) {
    tr = bf[ps[f = k]].c;
    }
    }
    for (k = 0; k < top; k++) {
    bf[ps[k]].c -= tr, bf[ps[k] ^ 1].c += tr;
    }
    res += tr;
    i = bf[ps[top = f]].x;
    }
    for (j = cur[i]; cur[i]; j = cur[i] = bf[cur[i]].nxt) {
    if (bf[j].c && dep[i] + 1 == dep[bf[j].y]) {
    break;
    }
    }
    if (cur[i]) {
    ps[top++] = cur[i];
    i = bf[cur[i]].y;
    } else {
    if (0 == top) {
    break;
    }
    dep[i] = -1;
    i = bf[ps[--top]].x;
    }
    }
    }
    return res;
    }

    void init(int m, int n) {
    int s = m * n;
    int t = s + 1;
    typec value;
    sum = 0;
    for (int i = 0; i < m; i++) {
    for (int j = 0; j < n; j++) {
    scanf("%d", &value);
    sum += value;
    if ((i + j) % 2 == 0) {
    addedge(s, i * n + j, value);
    if (i > 0) {
    addedge(i * n + j, (i - 1) * n + j, inf);
    }
    if (j > 0) {
    addedge(i * n + j, i * n + j - 1, inf);
    }
    if (i < m - 1) {
    addedge(i * n + j, (i + 1) * n + j, inf);
    }
    if (j < n - 1) {
    addedge(i * n + j, i * n + j + 1, inf);
    }
    } else {
    addedge(i * n + j, t, value);
    }
    }
    }
    }

    int main() {
    #ifndef ONLINE_JUDGE
    freopen("data.in", "r", stdin);
    #endif
    int n, m;
    while (scanf("%d%d", &m, &n) != EOF) {
    ne = 2;
    memset(head, 0, sizeof(head));
    init(m, n);
    printf("%d\n", sum - flow(m * n + 2, m * n, m * n + 1));
    }
    return 0;
    }



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  • 原文地址:https://www.cnblogs.com/moonbay/p/2199421.html
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