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