hdu 1856 More is better （并查集）

Problem - 1856

　　水题。离散化，然后求最大集合元素个数。

　　忘记压缩路径了，tle了很久。- -

代码如下：

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <map>

using namespace std;

const int N = 222222;
map<int, int> id;

struct MFS {
    int fa[N], sz[N], mxsz;
    void init() {
        for (int i = 0; i < N; i++) fa[i] = i, sz[i] = 1;
        mxsz = 1;
    }
    int find(int x) { return fa[x] = x == fa[x] ? x : find(fa[x]);}
    void merge(int x, int y) {
        int fx = find(x), fy = find(y);
        if (fx == fy) return ;
        fa[fx] = fy;
        sz[fy] += sz[fx];
        mxsz = max(mxsz, sz[fy]);
    }
} mfs;

int main() {
    int n, x, y;
    while (~scanf("%d", &n)) {
        mfs.init();
        id.clear();
        while (n--) {
            scanf("%d%d", &x, &y);
            if (id.find(x) == id.end()) id[x] = id.size();
            if (id.find(y) == id.end()) id[y] = id.size();
            mfs.merge(id[x], id[y]);
        }
        printf("%d
", mfs.mxsz);
    }
    return 0;
}

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

using namespace std;

const int N = 222222;
const int M = 11111111;

struct MFS {
    int fa[N], sz[N], mxsz;
    void init() { mxsz = 1;}
    int find(int x) { return fa[x] = fa[x] == x ? x : find(fa[x]);}
    void merge(int x, int y) {
        int fx = find(x);
        int fy = find(y);
        if (fx == fy) return ;
        if (sz[fx] > sz[fy]) {
            fa[fx] = fy;
            sz[fy] += sz[fx];
            mxsz = max(mxsz, sz[fy]);
        } else {
            fa[fy] = fx;
            sz[fx] += sz[fy];
            mxsz = max(mxsz, sz[fx]);
        }
    }
} mfs;

inline bool isdg(char x) { return '0' <= x && x <= '9';} 
void scan(int &x) {
    char ch;
    while (!isdg(ch = getchar())) ;
    x = ch - '0';
    while (isdg(ch = getchar())) x = x * 10 + ch - '0';
}

int id[M], rx[N], x[N >> 1], y[N >> 1];

int main() {
    int n;
    while (~scanf("%d", &n)) {
        mfs.init();
        for (int i = 0; i < n; i++) {
            //scanf("%d%d", &x[i], &y[i]);
            scan(x[i]), scan(y[i]);
            rx[i << 1] = x[i];
            rx[i << 1 | 1] = y[i];
        }
        sort(rx, rx + (n << 1));
        int m = unique(rx, rx + (n << 1)) - rx;
        for (int i = 0; i < m; i++) id[rx[i]] = i, mfs.sz[i] = 1, mfs.fa[i] = i;
        for (int i = 0; i < n; i++) {
            mfs.merge(id[x[i]], id[y[i]]);
        }
        printf("%d
", mfs.mxsz);
    }
    return 0;
}

——written by Lyon