牛客网：NC86 矩阵元素查找

暴力

import java.util.*;

public class Solution {
    public int[] findElement(int[][] mat, int n, int m, int x) {
        // write code here
        for(int i = 0; i < n; i++){
            for (int j = 0; j < m; j++){
                if (mat[i][j] == x){
                    return new int[]{i , j};
                }
            }
        }
        return null;
    }
}

使用贪心

import java.util.*;

public class Solution {
    public int[] findElement(int[][] mat, int n, int m, int x) {
        // write code here
        int i = n - 1, j = 0;
        while (i >= 0 && j < m){
            if (mat[i][j] == x) break;
            if (mat[i][j] > x) i--;
            else j++;
        }
        return new int[]{i, j};
    }
}

使用二分

import java.util.*;

public class Solution {
    public int[] findElement(int[][] mat, int n, int m, int x) {
        // write code here
        for (int i = 0; i < n; i++){
            if (mat[i][m - 1] < x) continue;
            int left = 0, right = m - 1;
            while (left <= right){
                int mid = (left + right) >> 1;
                if (mat[i][mid] == x) return new int[]{i , mid};
                if (mat[i][mid] < x) left = mid + 1;
                else right = mid - 1;
            }
        }
        return null;
    }
}