BZOJ1149 – [APIO2007][CTSC2007]风玲Mobiles

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#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <limits>
#define nlimit numeric_limits
using namespace std;
const int PSIZ = 1E5 + 1E3;
int N;
int L[PSIZ], R[PSIZ];

int maxd, mind;
void dfs(int cur, int dep) {
    if(cur == -1) { maxd = max(maxd, dep); mind = min(mind, dep); return; }
    dfs(L[cur], dep+1); dfs(R[cur], dep+1);
}

int ans = 0;
#define pack(a, b) ((a << 4) + b)
int solve(int cur, int dep) {
    int a, b;
    if(cur == -1) return (dep!=mind) + 1;
    a = solve(L[cur], dep+1);
    b = solve(R[cur], dep+1);
    switch(pack(a, b)) {
    case pack(1, 2):
    case pack(1, 3):
    case pack(3, 2): ans += 1; break;
    case pack(3, 3): printf("-1n"); exit(0); break;
    }

    return a|b;
}

void work() {
    maxd = nlimit<int>::min();
    mind = nlimit<int>::max();
    dfs(1, 0);

    if(maxd - mind >= 2) { printf("-1n"); exit(0); }
    if(maxd == mind) { printf("0n"); exit(0); }

    solve(1, 0);
}

int main() {
    scanf("%d", &N);

    for(int i=1;i<=N;i++) {
        scanf("%d %d", &L[i], &R[i]);
    }

    work();

    printf("%dn", ans);
}