2965. Find Missing and Repeated Values

 

You are given a 0-indexed 2D integer matrix grid of size n * n with values in the range [1, n2]. Each integer appears exactly once except a which appears twice and b which is missing. The task is to find the repeating and missing numbers a and b.

Return a 0-indexed integer array ans of size 2 where ans[0] equals to a and ans[1] equals to b.

 

Example 1:

Input: grid = [[1,3],[2,2]]
Output: [2,4]
Explanation: Number 2 is repeated and number 4 is missing so the answer is [2,4].

Example 2:

Input: grid = [[9,1,7],[8,9,2],[3,4,6]]
Output: [9,5]
Explanation: Number 9 is repeated and number 5 is missing so the answer is [9,5]. 

class Solution {

public int[] findMissingAndRepeatedValues(int[][] grid) {

int n = grid.length;

int[] res = new int[2];

Map<Integer,Integer> freqCount = new HashMap<>();

for(int i = 0;i<n;i++){

for(int j=0;j<n;j++){

freqCount.put(grid[i][j],freqCount.getOrDefault(grid[i][j],0)+1);

}

}

for(int i = 1;i<= n*n;i++){

int count = freqCount.getOrDefault(i,0);

if(count == 0){

res[1] = i;

}else if(count == 2){

res[0] = i;

}

}

return res;

}

}