poj_2385 Apple Catching (DP)

Please point me in the question.

Exercises

The topic conforms to the current optimal state from multiple optimal states, so it is a DP right, so the key is the definition of DP array and the recursive equation.

At the beginning, according to their own ideas, will be a succession of the same fruit drop merge,

DP Array Dp[i][j] Definition: The optimal result of reaching J position after I was transferred.

Recursion relationship: Dp[i][j] = max (Dp[i][j],dp[i-1][k]+get (k,j)) (k:i-1~j) Get function Gets the number of fruit corresponding to the current Apple tree between K,j.

The original intention for the fruit will be simple after the merger, three-layer for the loop, but the trouble, the data is weak, or too. After AC reference online ideas, found will be much simpler.

DP Array Dp[i][j] Definition: The optimal result of a J-time prior to I position (just the opposite ...). ）

Recursive relationship: dp[i][j] = max (Dp[i-1][j],dp[i-1][j-1]). Well understood, there are two possible ways to reach position I, one is to stay and not move, the other is just turn around and take the optimal solution. If it's just under the corresponding Apple tree, + +. A lot easier, 0ms is over.

To summarize the definition of DP is to see how the state changes, the current state from which states come, find the appropriate DP definition.

Reference Blog

Code implementation:

(Own code)

#include <iostream> #include <cstdio> #include <cstdlib> #include <cstring> #define LL Long     longusing namespace Std;const int MAX = 1010;int t,w;int res;int num[max];int dp[35][max];int get (int x,int y); int main () {    scanf ("%d%d", &t,&w);    res = 0;    int Last,tag;    int sum = 0;    memset (num,0,sizeof (sum));        for (int i = 0; i < T; i++) {scanf ("%d", &tag);        if (i = = 0) {num[sum]++;            } else{if (last = = tag) {num[sum]++;                } else{sum++;            num[sum]++;    }} last = tag;    } memset (Dp,0,sizeof (DP));    for (int i = 0; I <= sum; i++) {Dp[0][i] = get ( -1,i); } for (int i = 1, i <= W; i++) {for (int j = i; j <= Sum; j + +) {for (int k = i-1; k <= j-1 ;            k++) {Dp[i][j] = max (Dp[i][j],dp[i-1][k]+get (k,j)); }} res = max (dp[i][sum],res);    } printf ("%d\n", res); return 0;}    The uniform definition starts at the next position int get (int x,int y) {int tmp1 = 0;    int TMP2 = 0;        for (int i = x+1; I <= y; i++) {if ((i-x)%2 = = 0) {TMP1 + = Num[i];        } else{TMP2 + = Num[i]; }} return Max (TMP1,TMP2);}

(Another way to change the idea of a code)

 #include <iostream> #include <cstdio> #include <cstdlib> #include < Cstring> #define LL Long longusing namespace Std;const int MAX = 1010;int t,w;int res;int num[max];int dp[max][35];int m    Ain () {scanf ("%d%d", &t,&w);    res = 0;    Memset (Dp,0,sizeof (DP));    memset (num,0,sizeof (num));    for (int i = 1; I <= T; i++) {scanf ("%d", &num[i]);        } if (num[1] = = 1) {dp[1][0] = 1;    DP[1][1] = 0;        } else{Dp[1][1] = 1;    Dp[1][0] = 0; } for (int i = 2; I <= T, i++) {for (int j = 0; J <= I; j + +) {if (j = = 0) {DP I                [j] = dp[i-1][j]+num[i]%2;            Continue            } Dp[i][j] = max (dp[i-1][j],dp[i-1][j-1]);            if (num[i] = = j%2+1) {dp[i][j]++;    }}} for (int i = 0; I <= W; i++) {res = max (res,dp[t][i]);    } printf ("%d\n", res); return 0;} 

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poj_2385 Apple Catching (DP)