poj 2479 - Maximum sum

標籤：io   for   c   amp   r   bs   as   dp   poj   

題目：找到一個序列中的兩個連續段使得他們的和最大。

分析：dp，最大欄位和。雙向求最大欄位和，枚舉結束點找到加和最大值。

說明：與合唱隊形類似。（同poj2593）（2011-09-24 02:09）

#include <stdio.h>#include <stdlib.h>int data[ 50005 ];int asum[ 50005 ];int bsum[ 50005 ];void msum( int *D,int *A, int a, int b, int s ){    int sum = 0;    for ( int i = a ; i != b ; i += s ) {        if ( sum < 0 ) sum = 0;        sum += D[ i ];        A[ i ] = sum;    }    int max = A[ a ];    for ( int i = a+s ; i != b ; i += s )        if ( max < A[ i ] ) max = A[ i ];        else A[ i ] = max;}int main(){    int t,n;    while ( scanf("%d",&t) != EOF )     while ( t -- ) {        scanf("%d",&n);        for ( int i = 1 ; i <= n ; ++ i )            scanf("%d",&data[ i ]);                    msum( data, asum, 1, n, +1 );        msum( data, bsum, n, 1, -1 );        int    max = -20000;        for ( int i = 1 ; i <  n ; ++ i )            if ( max < asum[ i ] + bsum[ i+1 ] )                max = asum[ i ] + bsum[ i+1 ];                printf("%d\n",max);    }    return 0;} 

poj 2479 - Maximum sum