HDU 1502 Regular Words（大数+dp）

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题目地址：http://acm.hdu.edu.cn/showproblem.php?pid=1502

思路：dp[3*n][n][n][n]，第一维是长度，第2.3.4维是a,b,c的个数，写出的转移方程不是超Int就是超内存，java跑出的结果和别人AC代码跑出的结果相同，思路是对的

后来参考别人的思路又想了一个省空间的状态转移方程dp[i][j][k]=dp[i-1][j][k]+dp[i][j-1][k]+dp[i][j][k-1]，java的捕异常让人很烦啊

AC代码：

import java.io.*;import java.util.*;import java.math.BigInteger;public class Main {public static void main(String[] args) {// TODO Auto-generated method stubScanner cin = new Scanner(System.in);int n;while (cin.hasNextInt()) {n = cin.nextInt();BigInteger[][][] dp = new BigInteger[61][61][61];for(int i=0; i<=60; i++){for(int j=0; j<=60; j++){for(int k=0; k<=60; k++){dp[i][j][k] = BigInteger.ZERO;}}}dp[1][0][0] = BigInteger.ONE;dp[1][1][0] = BigInteger.ONE;dp[1][1][1] = BigInteger.ONE;for(int i=2; i<=n; i++){for(int j=0; j<=n; j++){if(j > i)continue;for(int k=0; k<=n; k++){if(k > j)continue;dp[i][j][k] = dp[i][j][k].add(dp[i-1][j][k]);if(j - 1 < i && j - 1 >= 0)dp[i][j][k] = dp[i][j][k].add(dp[i][j-1][k]);if(k - 1 < j && k - 1 >= 0)dp[i][j][k] = dp[i][j][k].add(dp[i][j][k-1]);}}}System.out.println(dp[n][n][n]+"");System.out.println("");}}}

错误代码1：

#include <iostream>#include <cstdio>#include <cstdlib>#include <algorithm>#include <queue>#include <stack>#include <map>#include <cstring>#include <climits>#include <cmath>#include <cctype>const int inf = 0x3f3f3f3f;//1061109567typedef long long LL;#define lson l,m,rt<<1#define rson m+1,r,rt<<1|1using namespace std;int dp[200][60][60][60];int main(){    int n;    while(scanf("%d",&n) != EOF)    {        memset(dp,0,sizeof(dp));        dp[1][1][0][0] = 1;        for(int i=2; i<=3*n; i++)        {            for(int j=1; j<=n; j++)            {                for(int k=0; k<=n; k++)                {                    if(k > j)                        continue;                    for(int l=0; l<=n; l++)                    {                        if(l > k)                            continue;                        if(j + k + l != i-1)                            continue;                        if(j + 1 <= n)                            dp[i][j+1][k][l] += dp[i-1][j][k][l];                        if(k < j && k + 1 <= n)                            dp[i][j][k+1][l] += dp[i-1][j][k][l];                        if(l < k && l + 1 <= n)                            dp[i][j][k][l+1] += dp[i-1][j][k][l];                    }                }            }        }        printf("%d\n\n",dp[3*n][n][n][n]);    }    return 0;}

直接超了int，改用Java写

错误代码2：

import java.io.*;import java.util.*;import java.math.BigInteger;public class Test4 {public static void main(String[] args) {// TODO Auto-generated method stubScanner cin = new Scanner(System.in);int n;while(cin.hasNextInt()){n = cin.nextInt();BigInteger[][][][] dp = new BigInteger[181][61][61][61];for(int i=1; i<=180; i++){for(int j=0; j<=60; j++){for(int k=0; k<=60; k++){if(k > j)continue;for(int l=0; l<=60; l++){if(l > k)continue;dp[i][j][k][l] = BigInteger.ZERO;}}}}dp[1][1][0][0] = BigInteger.ONE;for(int i=2; i<=3*n; i++){for(int j=1; j<=n; j++){for(int k=0; k<=n; k++){if(k > j)continue;for(int l=0; l<=n; l++){if(l > k)continue;if(j + k + l != i-1)continue;if(j+1 <=n)dp[i][j+1][k][l] = dp[i][j+1][k][l].add(dp[i-1][j][k][l]);if(k < j && k+1 <= n)dp[i][j][k+1][l] = dp[i][j][k+1][l].add(dp[i-1][j][k][l]);if(l < k && l+1 <= n)dp[i][j][k][l+1] = dp[i][j][k][l+1].add(dp[i-1][j][k][l]);}}}}System.out.println(dp[3*n][n][n][n]+"");System.out.print("");}}}

超内存了

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