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ZOJ 1074 To the Max (DP)
Problem
Given a two-dimensional array of positive and negative integers, a sub-rectangle is any contiguous sub-array of size 1 x 1 or greater located within the whole array. The sum of a rectangle is the sum of all the elements in that rectangle. In this problem the sub-rectangle with the largest sum is referred to as the maximal sub-rectangle.
As an example, the maximal sub-rectangle of the array:
0 -2 -7 0
9 2 -6 2
-4 1 -4 1
-1 8 0 -2
is in the lower left corner:
9 2
-4 1
-1 8
and has a sum of 15.
The input consists of an N x N array of integers. The input begins with a single positive integer N on a line by itself, indicating the size of the square two-dimensional array. This is followed by N 2 integers separated by whitespace (spaces and newlines). These are the N 2 integers of the array, presented in row-major order. That is, all numbers in the first row, left to right, then all numbers in the second row, left to right, etc. N may be as large as 100. The numbers in the array will be in the range [-127,127].
Output
Output the sum of the maximal sub-rectangle.
Example
Input
4
0 -2 -7 0 9 2 -6 2
-4 1 -4 1 -1
8 0 -2
Output
15
水,直接水过。
#include<iostream> #include<cstdio> #include<cstring> #include<algorithm> #include<limits.h> using namespace std; int a[110][110]; int n,x; int main() { int sum,maxn; while(~scanf("%d",&n)) { memset(a,0,sizeof(a)); for(int i=1;i<=n;i++) { for(int j=1;j<=n;j++) { scanf("%d",&x); a[i][j]=a[i-1][j]+x; } } maxn=0; for(int i=1;i<=n;i++) { for(int j=i;j<=n;j++) { sum=0; for(int k=1;k<=n;k++) { int t=a[j][k]-a[i-1][k]; sum+=t; // cout<<"fuck "<<sum<<endl; if(sum<0) sum=0; if(sum>maxn) maxn=sum; } } } printf("%d\n",maxn); } return 0; }