这题比较简单，注意路径压缩即可。

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AC代码

//#define LOCAL
#include <stdio.h>
#include <algorithm>
using namespace std;
const int maxn = 20000+5;
int par[maxn], dis[maxn];

void init(int n) {
    for(int i = 0; i <= n; i++) {
        par[i] = i;
        dis[i] = 0;
    }
}

int findRoot(int x) {
    if(x == par[x]) {
        return x;
    } else {
        int root = findRoot(par[x]);
        dis[x] += dis[par[x]];
        return par[x] = root;
    }
}

int main() {
#ifdef LOCAL
    freopen("data.in", "r", stdin);
    freopen("data.out", "w", stdout);
#endif // LOCAL

    int T, n;
    scanf("%d", &T);
    while(T--) {
        scanf("%d", &n);
        init(n);
        char cmd[10];
        int x, y;
        while(scanf("%s", cmd) == 1 && cmd[0] != 'O') {
            char tag = cmd[0];
            if(tag == 'E') {
                scanf("%d", &x);
                findRoot(x);
                printf("%d\n", dis[x]);
            } else {
                scanf("%d%d", &x, &y);
                par[x] = y;
                dis[x] = abs(x-y) % 1000;
            }
        }

    }
    return 0;
}

如有不当之处欢迎指出！