1263F - Economic Difficulties - CodeForces Solution


data structures dfs and similar dp flows graphs trees *2400

Please click on ads to support us..

C++ Code:

#include <bits/stdc++.h>

#define ll long long
using namespace std;

const int N = 2005;
const int M = 15;

vector<int> adj[N][2];

int device[N][2];

int depth[N][2],anc[N][M][2];

//test

void dfs(int node,int par,int parity) {

    anc[node][0][parity] = par;
    for(int i=1;i<M;++i) {
        anc[node][i][parity] = anc[anc[node][i-1][parity]][i-1][parity];
    }

    for(int ch : adj[node][parity]) {
        if(ch!=par) {
            depth[ch][parity] = depth[node][parity] + 1;
            dfs(ch,node,parity);
        }
    }
}

pair<int,int> getAnc(int x,int y,int parity) {
    int ret = 0;
    if(depth[x][parity]<depth[y][parity]) {
        swap(x,y);
    }
    ret = depth[x][parity] - depth[y][parity];
    for(int i=0;i<M;++i) {
        if(ret&(1<<i)) {
            x = anc[x][i][parity];
        }
    }
    if(x!=y) {
        for(int i=M-1;i>=0;--i) {
            if(anc[x][i][parity]!=anc[y][i][parity]) {
                ret += 2*(1<<i);
                x = anc[x][i][parity];
                y = anc[y][i][parity];
            }
        }
        ret += 2;
        x = anc[x][0][parity];
        y = anc[y][0][parity];
    }
    assert(x==y);
    return {x,ret};
}

int preSet[N][N][2];
int dp[N][N][2][2];



int solveDp(int cur,int last,int up,int iter,int n) {
    if(cur>n) {
        return 0;
    }
    int &ret = dp[cur][last][up][iter];
    if(ret!=-1) {
        return ret;
    }
    ret = 1e9;

    if(iter) {
        ret = min(ret, solveDp(cur+1,last,up,iter,n) + preSet[cur-1][cur][up]);
        ret = min(ret, solveDp(cur+1,cur-1,up^1,1,n) + preSet[last][cur][up^1]);
    } else {
        assert(0);
    }
    return ret;
}

void solve2() {
    int n,a,b;
    scanf("%d ",&n);

    scanf("%d ",&a);
    for(int i=2;i<=a;++i) {
        int p;
        scanf("%d ",&p);
        adj[p][0].push_back(i);
    }
    for(int i=1;i<=n;++i) {
        scanf("%d ",&device[i][0]);
    }

    scanf("%d ",&b);

    for(int i=2;i<=b;++i) {
        int p;
        scanf("%d ",&p);
        adj[p][1].push_back(i);
    }
    for(int i=1;i<=n;++i) {
        scanf("%d ",&device[i][1]);
    }
    device[0][0] = device[0][1] = 1;
    dfs(1,0,0);
    dfs(1,0,1);

    for(int up=0;up<2;++up) {
        for(int i=0;i<=n;++i) {
            for(int j=0;j<=n;++j) {
                int lca = getAnc(device[i][up], device[j][up],up).first;
                preSet[i][j][up] = depth[device[j][up]][up] - depth[lca][up];
            }
        }
    }
    memset(dp,-1,sizeof(dp));
    printf("%d\n", a+b-2 - min(solveDp(1,0,1,1,n), solveDp(1,0,0,1,n)));
}

void solve() {
    // init();
    // int t;
    // scanf("%d",&t);
    // while(t--)
    solve2();
}

inline bool exists_test0 (const std::string& name);
inline bool exists_test1 (const std::string& name);
int main() {
  solve();
  return 0;
}

/*
0. Enough array nsize? Enough array nsize? Integer overflow?

1. Think TWICE, Code ONCE!
Are there any counterexamples to your algo?

2. Be careful about the BOUNDARIES!
N=1? P=1? Something about 0?

3. Do not make STUPID MISTAKES!
Time complexity? Memory usage? Precision error?

4. Be careful to use wrong variable.
*/
inline bool exists_test0 (const std::string& name) {
    ifstream f(name.c_str());
    return f.good();
}

inline bool exists_test1 (const std::string& name) {
    if (FILE *file = fopen(name.c_str(), "r")) {
        fclose(file);
        return true;
    } else {
        return false;
    }
}


Comments

Submit
0 Comments
More Questions

1365. How Many Numbers Are Smaller Than the Current Number
771. Jewels and Stones
1512. Number of Good Pairs
672. Richest Customer Wealth
1470. Shuffle the Array
1431. Kids With the Greatest Number of Candies
1480. Running Sum of 1d Array
682. Baseball Game
496. Next Greater Element I
232. Implement Queue using Stacks
844. Backspace String Compare
20. Valid Parentheses
746. Min Cost Climbing Stairs
392. Is Subsequence
70. Climbing Stairs
53. Maximum Subarray
1527A. And Then There Were K
1689. Partitioning Into Minimum Number Of Deci-Binary Numbers
318. Maximum Product of Word Lengths
448. Find All Numbers Disappeared in an Array
1155. Number of Dice Rolls With Target Sum
415. Add Strings
22. Generate Parentheses
13. Roman to Integer
2. Add Two Numbers
515. Find Largest Value in Each Tree Row
345. Reverse Vowels of a String
628. Maximum Product of Three Numbers
1526A - Mean Inequality
1526B - I Hate 1111