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Solution661.java
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Solution661.java
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package leetcode.prefixsum.matrix;
import java.util.Arrays;
public class Solution661 {
public static void main(String[] args) {
System.out.println(Arrays.deepToString(new Solution661().imageSmoother(new int[][]{
new int[]{1, 2, 3},
new int[]{4, 5, 6},
new int[]{7, 8, 9},
new int[]{10, 11, 12}
})));
}
public int[][] imageSmoother(int[][] img) {
int[][] preSum = new int[img.length + 1][img[0].length + 1];
for (int i = 1; i < preSum.length; i++) {
for (int j = 1; j < preSum[0].length; j++) {
preSum[i][j] = img[i - 1][j - 1] + preSum[i - 1][j] + preSum[i][j - 1] - preSum[i - 1][j - 1];
}
}
int[][] res = new int[img.length][img[0].length];
for (int i = 0; i < res.length; i++) {
for (int j = 0; j < res[0].length; j++) {
int a = Math.max(0, i - 1), b = Math.max(0, j - 1);
int c = Math.min(res.length - 1, i + 1), d = Math.min(res[0].length - 1, j + 1);
int area = (c - a + 1) * (d - b + 1);
res[i][j] = (preSum[c + 1][d + 1] - preSum[a][d + 1] - preSum[c + 1][b] + preSum[a][b]) / area;
}
}
return res;
}
}