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package class01;
public class Code05_LongestIncreasingPath {
public static int longestIncreasingPath1(int[][] matrix) {
int ans = 0;
int N = matrix.length;
int M = matrix[0].length;
for (int i = 0; i < N; i++) {
for (int j = 0; j < M; j++) {
ans = Math.max(ans, process1(matrix, i, j));
}
}
return ans;
}
// 从m[i][j]开始走,走出来的最长递增链,返回!
public static int process1(int[][] m, int i, int j) {
int up = i > 0 && m[i][j] < m[i - 1][j] ? process1(m, i - 1, j) : 0;
int down = i < (m.length - 1) && m[i][j] < m[i + 1][j] ? process1(m, i + 1, j) : 0;
int left = j > 0 && m[i][j] < m[i][j - 1] ? process1(m, i, j - 1) : 0;
int right = j < (m[0].length - 1) && m[i][j] < m[i][j + 1] ? process1(m, i, j + 1) : 0;
return Math.max(Math.max(up, down), Math.max(left, right)) + 1;
}
public static int longestIncreasingPath2(int[][] matrix) {
int ans = 0;
int N = matrix.length;
int M = matrix[0].length;
int[][] dp = new int[N][M];
for (int i = 0; i < N; i++) {
for (int j = 0; j < M; j++) {
ans = Math.max(ans, process2(matrix, i, j, dp));
}
}
return ans;
}
// 从m[i][j]开始走,走出来的最长递增链,返回!
public static int process2(int[][] m, int i, int j, int[][] dp) {
if (dp[i][j] != 0) {
return dp[i][j];
}
// (i,j)不越界
int up = i > 0 && m[i][j] < m[i - 1][j] ? process2(m, i - 1, j, dp) : 0;
int down = i < (m.length - 1) && m[i][j] < m[i + 1][j] ? process2(m, i + 1, j, dp) : 0;
int left = j > 0 && m[i][j] < m[i][j - 1] ? process2(m, i, j - 1, dp) : 0;
int right = j < (m[0].length - 1) && m[i][j] < m[i][j + 1] ? process2(m, i, j + 1, dp) : 0;
int ans = Math.max(Math.max(up, down), Math.max(left, right)) + 1;
dp[i][j] = ans;
return ans;
}
}