docs: 添加仓库地址到README；chore: 整理实验分析；feat: Kruskal最小生成树与图存储结构

exercise/39.c

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+#include <stdio.h>
+#include <stdlib.h>
+
+int main(void) {
+    int n, m;
+    if (scanf("%d %d", &n, &m) != 2) return 0;
+    int *a = (int*)malloc((size_t)(n + 1) * sizeof(int));
+    for (int i = 1; i <= n; ++i) scanf("%d", &a[i]);
+    int *cnt = (int*)calloc((size_t)(m + 1), sizeof(int));
+    int covered = 0;
+    int l = 1;
+    int best_l = 1, best_r = n;
+    int best_len = n;
+    for (int r = 1; r <= n; ++r) {
+        int c = a[r];
+        if (cnt[c] == 0) ++covered;
+        ++cnt[c];
+        if (covered == m) {
+            while (cnt[a[l]] > 1) { --cnt[a[l]]; ++l; }
+            int len = r - l + 1;
+            if (len < best_len || (len == best_len && l < best_l)) {
+                best_len = len; best_l = l; best_r = r;
+            }
+        }
+    }
+    printf("%d %d\n", best_l, best_r);
+    free(cnt);
+    free(a);
+    return 0;
+}