https://leetcode-cn.com/problems/edit-distance/

思路一：动态规划来做

public int minDistance(String word1, String word2) {
if (word1 == null || word2 == null) return 0;
char[] cs1 = word1.toCharArray();
char[] cs2 = word2.toCharArray();
int[][] dp = new int[cs1.length + 1][cs2.length + 1];
dp[0][0] = 0;
// 第0列
for (int i = 1; i <= cs1.length; i++) {
dp[i][0] = i;
}
// 第0行
for (int j = 1; j <= cs2.length; j++) {
dp[0][j] = j;
}
// 其他行其他列
for (int i = 1; i <= cs1.length; i++) {
for (int j = 1; j <= cs2.length; j++) {
int top = dp[i - 1][j] + 1;
int left = dp[i][j - 1] + 1;
int leftTop = dp[i - 1][j - 1];
if (cs1[i - 1] != cs2[j - 1]) {
leftTop++;
}
dp[i][j] = Math.min(Math.min(top, left), leftTop);
}
}
return dp[cs1.length][cs2.length];
}