func_code_string: #include <bits/stdc++.h>   using namespace std;   int n, m, T, fa[500005], top, st[500005 << 2], d[500005], a[500005];   struct E {     int x, y, l, r;   } e[500005];   int Getfa(int x) {     while (fa[x] != x) x = fa[x];     return x;   }   int col(int x) {     int now = 0;     while (fa[x] != x) now ^= a[x], x = fa[x];     return now;   }   void link(int x, int y, int D) {     if (d[x] > d[y]) swap(x, y);     if (d[x] == d[y]) d[y]++, st[++top] = -y;     fa[x] = y;     a[x] = D;     st[++top] = x;   }   void RE(int t) {     for (; top > t; top--)       if (st[top] < 0)         d[-st[top]]--;       else         fa[st[top]] = st[top], a[st[top]] = 0;   }   void work(int l, int r, int k) {     int mid = (l + r) >> 1, now = top;     for (int i = 1; i <= k; i++)       if (e[i].l <= l && r <= e[i].r) {         int u = Getfa(e[i].x), v = Getfa(e[i].y);         if (u != v)           link(u, v, col(e[i].x) == col(e[i].y));         else if (col(e[i].x) == col(e[i].y)) {           for (int i = l; i <= r; i++) puts( NO );           RE(now);           return;         }         swap(e[k--], e[i--]);       }     if (l == r)       puts( YES );     else {       int i, j;       for (i = 1, j = 0; i <= k; i++)         if (e[i].l <= mid) swap(e[i], e[++j]);       work(l, mid, j);       for (i = 1, j = 0; i <= k; i++)         if (e[i].r > mid) swap(e[i], e[++j]);       work(mid + 1, r, j);     }     RE(now);   }   map<int, int> M[500005];   int main() {     scanf( %d%d , &n, &T);     for (int i = 1; i <= T; i++) {       int x, y;       scanf( %d%d , &x, &y);       if (x > y) swap(x, y);       if (M[x][y])         e[M[x][y]].r = i - 1, M[x][y] = 0;       else {         M[x][y] = ++m;         e[m].x = x;         e[m].y = y;         e[m].l = i - 1;         e[m].r = T;       }     }     for (int i = 1; i <= m; i++) {       if (++e[i].l > e[i].r) {         i--, m--;         assert(false);       }     }     for (int i = 1; i <= n; i++) fa[i] = i, d[i] = 1;     work(1, T, m);     return 0;   }   