编程之美2.15子数组之和的最大值(二维)Java版

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/* * To change this license header, choose License Headers in Project Properties. * To change this template file, choose Tools | Templates * and open the template in the editor. */package Test;/** * * 2.15 子数组之和的最大值(二维) */public class SearchArrayMaxSum2 {    public static void main(String[] args) {        int[][] arry = new int[][]{{2, -4, 1, -6, 7, 10}, {4, 3, 5, -8, 11, -9},{6,-3,9,-7,-1,-4}};        //解法一        int num1 = searchMax1(arry, arry.length, arry[0].length);        System.out.println("num1 ="+num1);        //解法二        int num2 = searchMax2(arry,arry.length,arry[0].length);        System.out.println("num2 ="+num2);    }    private static int searchMax1(int[][] arry, int n, int m) {        int[][] ps = new int[n + 1][m + 1];        //预处理        for (int i = 0; i <= n; i++) {            ps[i][0] = 0;        }        for (int j = 0; j <= m; j++) {            ps[0][j] = 0;        }        for (int i = 1; i <= n; i++) {            for (int j = 1; j <= m; j++) {                ps[i][j] = ps[i - 1][j] + ps[i][j - 1] - ps[i - 1][j - 1] + arry[i - 1][j - 1];            }        }               Integer maxsum = null;        for (int i_min = 1; i_min <= n; i_min++) {            for (int i_max = i_min; i_max <= n; i_max++) {                for (int j_min = 1; j_min <= m; j_min++) {                    for (int j_max = j_min; j_max <= m; j_max++) {                        int sum = ps[i_max][j_max] - ps[i_min - 1][j_max] - ps[i_max][j_min - 1] + ps[i_min - 1][j_min - 1];                        if (maxsum == null || sum > maxsum) {                            if (maxsum == null) {                                maxsum = new Integer(sum);                            }                            maxsum = sum;                        }                    }                }            }        }        return maxsum;    }    private static int searchMax2(int[][] arry, int n, int m) {         int[][] ps = new int[n + 1][m + 1];        //预处理        for (int i = 0; i <= n; i++) {            ps[i][0] = 0;        }        for (int j = 0; j <= m; j++) {            ps[0][j] = 0;        }        for (int i = 1; i <= n; i++) {            for (int j = 1; j <= m; j++) {                ps[i][j] = ps[i - 1][j] + ps[i][j - 1] - ps[i - 1][j - 1] + arry[i - 1][j - 1];            }        }        Integer maxsum = null;        for(int a =1;a<=n;a++){            for(int c =a ;c<=n;c++){                int Start = ps[c][m]-ps[a-1][m]-ps[c][m-1]+ps[a-1][m-1];                int All = ps[c][m]-ps[a-1][m]-ps[c][m-1]+ps[a-1][m-1];                for(int i =m-1;i>=1;i--){                    if(Start < 0)                        Start =0;                    Start +=ps[c][i]-ps[a-1][i]-ps[c][i-1]+ps[a-1][i-1];                    if(Start > All)                        All = Start;                                    }                if(maxsum == null || All > maxsum){                    if(maxsum == null)                        maxsum = new Integer(All);                    maxsum = All;                }            }        }        return maxsum;    }}
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