leetcode 第139场周赛

题目编号对应1071-1074

rank：https://leetcode.com/contest/weekly-contest-139/ranking

1071:枚举约数

package com.netease.music.leetcode;

/**
 * Created by dezhonger on 2019/6/3
 */
public class Leetcode1071 {
    public static void main(String[] args) {
        System.out.println(new Leetcode1071().gcdOfStrings("abcabc", "abc"));
    }
    int gcd(int a, int b) {
        return b == 0 ? a : gcd(b, a % b);
    }

    boolean check(String s1, String s2, int g) {
        String s = s1.substring(0, g);
        if (check(s, s1) && check(s, s2)) return true;
        return false;
    }

    private boolean check(String s, String s1) {
        int g = s.length();
        for (int i = 0; i < s1.length(); i += g) {
            if (!s.equals(s1.substring(i, i + g))) {
                return false;
            }
        }
        return true;
    }


    public String gcdOfStrings(String str1, String str2) {
        int len1 = str1.length();
        int len2 = str2.length();
        int g = gcd(len1, len2);
        int res = 0;
        for (int i = g; i >= 1; i--) {
            if (g % i == 0 && check(str1, str2, i)) {
                res = Math.max(res, i);
                break;
            }
        }
        if (res == 0) return "";
        else return str1.substring(0, res);
    }
}

1072：贪心

package com.netease.music.leetcode;

import java.util.Arrays;

/**
 * Created by dezhonger on 2019/6/3
 */
public class Leetcode1072 {
    public int maxEqualRowsAfterFlips(int[][] matrix) {
        int n = matrix.length;
        int m = matrix[0].length;
        int res = 1;
        for (int i = 0; i < n; i++) {
            int c = 1;
            for (int j = i + 1; j < n; j++) {
                if (Arrays.equals(matrix[i], matrix[j])) c++;
                else {
                    boolean f = true;
                    for (int k = 0; k < m; k++) {
                        if (matrix[i][k] + matrix[j][k] != 1) {
                            f = false;
                            break;
                        }
                    }
                    if (f) c++;
                }
            }
            res = Math.max(res, c);
        }
        return res;
    }
}

1073：负数进位制 （似乎和这个有点像https://leetcode.com/problems/convert-to-base-2/）

https://leetcode-cn.com/contest/weekly-contest-130

这个负数进位制的不太会。。

 

1074:二维矩阵和，枚举两行，然后枚举列

package com.netease.music.leetcode;

import java.util.HashMap;
import java.util.Map;

/**
 * Created by dezhonger on 2019/6/3
 */
public class Leetcode1074 {
    public int numSubmatrixSumTarget(int[][] a, int target) {
        int n = a.length;
        int m = a[0].length;
        int[][] cum = new int[n + 1][m + 1];
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++) {
                cum[i + 1][j + 1] = cum[i + 1][j] + cum[i][j + 1] - cum[i][j] + a[i][j];
            }
        }

        int ans = 0;
        for (int i = 0; i < n; i++) {
            for (int j = i; j < n; j++) {
                Map map = new HashMap<>();
                for (int k = 0; k <= m; k++) {
                    int v = cum[j + 1][k] - cum[i][k];
                    if (map.containsKey(v - target)) {
                        ans += map.get(v - target);
                    }
                    if (map.containsKey(v)) {
                        map.put(v, map.get(v) + 1);
                    } else {
                        map.put(v, 1);
                    }
                }
            }
        }
        return ans;
    }
}