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LC63_unique_paths_ii.java
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42 lines (40 loc) · 1.21 KB
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package Week06;
public class LC63_unique_paths_ii {
//加一个长度，判断前一数不是障碍时，计算dp
public int uniquePathsWithObstacles(int[][] obstacleGrid) {
if (obstacleGrid == null || obstacleGrid.length==0){
return 0;
}
int m = obstacleGrid.length;
int n = obstacleGrid[0].length;
int[][] dp = new int[m+1][n+1];
dp[0][1]=1;
for (int i=1;i<=m;i++){
for (int j=1;j<=n;j++){
if (obstacleGrid[i-1][j-1] == 0){
dp[i][j] = dp[i][j-1] + dp[i-1][j];
}
}
}
return dp[m][n];
}
/*必须画图加深理解
* 遇到1时，此路不通，dp =0
* */
public int uniquePathsWithObstacles_2(int[][] obstacleGrid) {
int m = obstacleGrid.length;
int n = obstacleGrid[0].length;
int[] dp = new int[n + 1];
dp[1] = 1;
for (int i = 0; i < m; i++) {
for (int j = 1; j <= n; j++) {
if (obstacleGrid[i][j - 1] == 1) {
dp[j] = 0;
} else {
dp[j] += dp[j - 1];
}
}
}
return dp[n];
}
}